feat: add iCalendar demo feature

.devcontainer/Dockerfile

@@ -84,12 +84,19 @@ RUN sh -c "$(wget -O- https://github.com/deluan/zsh-in-docker/releases/download/
 RUN npm install -g \
   corepack \
   @antfu/ni \
+  playwright \
   @anthropic-ai/claude-code
 
-# Copy and set up firewall script
-COPY init-firewall.sh /usr/local/bin/
+# install playwright browsers
 USER root
-RUN chmod +x /usr/local/bin/init-firewall.sh && \
-  echo "node ALL=(root) NOPASSWD: /usr/local/bin/init-firewall.sh" > /etc/sudoers.d/node-firewall && \
-  chmod 0440 /etc/sudoers.d/node-firewall
+RUN npm exec playwright install-deps
+USER node
+RUN npm exec playwright install
+
+# Copy and set up init scripts
+COPY node-init.sh init-firewall.sh install-playwright.sh /usr/local/bin/
+USER root
+RUN chmod +x /usr/local/bin/node-init.sh && \
+  echo "node ALL=(root) NOPASSWD: /usr/local/bin/node-init.sh" > /etc/sudoers.d/node-init && \
+  chmod 0440 /etc/sudoers.d/node-init
 USER node

.devcontainer/devcontainer.json

@@ -3,7 +3,7 @@
   "build": {
     "dockerfile": "Dockerfile",
     "args": {
-      "TZ": "${localEnv:TZ:America/Los_Angeles}"
+      "TZ": "${localEnv:TZ:Europe/Zurich}"
     }
   },
   "runArgs": [
@@ -57,5 +57,5 @@
   },
   "workspaceMount": "source=${localWorkspaceFolder},target=/workspace,type=bind,consistency=delegated",
   "workspaceFolder": "/workspace",
-  "postCreateCommand": "sudo /usr/local/bin/init-firewall.sh"
+  "postCreateCommand": "sudo /usr/local/bin/node-init.sh"
 }

.devcontainer/init-firewall.sh

@@ -53,6 +53,7 @@ done < <(echo "$gh_ranges" | jq -r '(.web + .api + .git)[]' | aggregate -q)
 # Resolve and add other allowed domains
 for domain in \
     "registry.npmjs.org" \
+    "chatgpt.com" \
     "api.anthropic.com" \
     "sentry.io" \
     "statsig.anthropic.com" \

.devcontainer/install-playwright.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -uo pipefail 
+
+echo "Installing Playwright browsers"
+
+npm i -g corepack && pnpm -v && \
+cd /workspace/packages/ && \
+pnpm install && \
+cd /workspace/packages/e2e-tests/ && \
+pnpm exec playwright install-deps && \
+sudo -u node pnpm exec playwright install && \
+echo "OK. Playwright browsers installed successfully."

.devcontainer/node-init.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+bash /usr/local/bin/install-playwright.sh
+
+bash /usr/local/bin/init-firewall.sh

.gitignore

@@ -73,3 +73,4 @@ typings/
 /tmp/
 /.pnpm-store/
 .DS_Store
+.claude/settings.local.json

AGENTS.md

@@ -0,0 +1,252 @@
+# AI Agent Guidelines
+
+_Vendor-neutral instructions for AI coding assistants (GitHub Copilot, Claude, Cursor, etc.)_
+
+## Key Rules
+
+1. **Follow existing patterns** - Look at neighboring code before implementing
+2. **Test everything** - Every feature needs unit tests AND E2E tests
+3. **Document decisions** - Explain WHY, not just WHAT
+4. **Keep it simple** - This is a demo project, avoid over-engineering
+5. **Security first** - Even demos should follow security best practices
+
+## Coding Standards
+
+### TypeScript Style
+
+- Use 2-space indentation for all files
+- Use explicit return types for functions
+- Use type imports with the `type` keyword
+- Use `type` for object shapes and primitives
+- NEVER use enums - use simple string unions instead
+- Prefer const assertions for literal types
+- Prefer `type` over `interface` for object types
+
+### Naming Conventions
+
+- **Variables, parameters, functions**: camelCase
+- **Classes, interfaces, types**: PascalCase
+- **Constants**: UPPER_CASE
+- **Files**: kebab-case for utilities, PascalCase for components/types
+- **Folders**: kebab-case
+
+### File Organization
+
+- One export per file when possible
+- Group related functionality in directories
+- Use index.ts files to re-export from directories
+- Keep files focused and under 300 lines when possible
+- Routes go in `/src/routes/` with subdirectories for organization
+- Types go in `/src/types/` as separate files
+- Unit tests are colocated as `*.test.ts` files
+- E2E tests go in `/packages/e2e-tests/`
+- Feature docs go in `/docs/features/`
+
+## Commit Messages
+
+```
+feat: add calendar subscription endpoint
+
+Implements RFC 5545 compliant iCalendar feed to test
+client compatibility across different calendar apps.
+
+Fixes #123
+```
+
+- First line: `<type>: <description>` (lowercase, ≤72 chars)
+- Types: `feat`, `fix`, `docs`, `test`, `refactor`, `chore`
+- Body: Explain WHY the change was made
+- Reference issues with `Fixes #123` or `Relates to #123`
+- Create feature branches as `feat/feature-name`
+- If GPG issues: `git commit --no-gpg-sign -m "message"`
+
+## Documentation Standards
+
+1. Every module should include JSDoc comments for all exported functions, classes, and interfaces
+2. Include parameter descriptions, return type descriptions, and examples
+3. Document thrown exceptions
+4. Update relevant documentation when changing functionality
+
+## Testing Guidelines
+
+### Unit Tests
+
+- Test files should be colocated with source files as `*.test.ts`
+- ALWAYS use Node.js built-in test runner (not Jest, Vitest, etc.)
+- Focus on testing business logic and edge cases
+- Use descriptive test names that explain the expected behavior
+
+### E2E Tests
+
+- Located in `/packages/e2e-tests/`
+- Use Cypress for browser automation (or Playwright for BDD approach)
+- Test user flows and integration between components
+- Include visual regression tests where appropriate
+
+#### E2E Framework Migration Guidelines
+
+When migrating between test frameworks:
+1. **Check Node.js version requirements** - Some features require specific versions
+2. **Verify package versions exist** before adding to package.json
+3. **Read all files before editing** - Even if you know the content
+4. **Update CI/CD workflows** - Located in `.github/workflows/`
+5. **Test locally first** when possible
+
+#### BDD Testing Pattern
+
+If using Playwright with BDD:
+- Write features in Gherkin syntax in `/features/` directory
+- Implement step definitions in `/steps/` directory
+- Use Page Object Model in `/pages/` directory
+- Use `createBdd()` pattern for importing Given/When/Then
+- Generate test files with `pnpm run generate` before running tests
+
+## Error Handling
+
+1. Use descriptive error messages
+2. Include context in error messages
+3. Prefer explicit error handling over try-catch for expected errors
+4. Log errors appropriately without exposing sensitive information
+
+## Code Review Checklist
+
+When reviewing or writing code, ensure:
+
+- [ ] Code follows the established patterns in the codebase
+- [ ] New features include appropriate tests
+- [ ] Documentation is updated where necessary
+- [ ] No console.log statements in production code
+- [ ] Error cases are handled appropriately
+- [ ] Security considerations have been addressed
+
+## Dependencies
+
+**ALWAYS prefer built-in Node.js modules over external packages**
+
+When adding dependencies:
+1. Justify why it's needed in the PR
+2. Pin exact version (no ^ or ~)
+3. Check bundle size impact
+4. Verify license compatibility
+
+Example justification:
+```
+Adding ical-generator@9.0.0:
+- Needed for RFC 5545 compliant calendar generation
+- No suitable Node.js built-in alternative
+- MIT licensed, 45KB minified
+```
+
+## Demo Development Process
+
+### When Adding New Demo Features
+1. ALWAYS create feature documentation first in `/docs/features/`
+2. ALWAYS implement types before implementation in `/src/types/`
+3. ALWAYS add both unit tests and E2E tests
+4. ALWAYS link new demos from the homepage
+5. ALWAYS test with multiple browsers/clients
+6. ALWAYS document vendor-specific workarounds
+
+### Demo Requirements Checklist
+- [ ] Single concept focus (one demo = one feature)
+- [ ] Live interactive demo at `/demos/<feature>`
+- [ ] API endpoint documented with curl examples
+- [ ] Client compatibility table in docs
+- [ ] Links to official specs (RFC, W3C, etc.)
+- [ ] E2E tests covering happy path + edge cases
+- [ ] Vendor workarounds documented with examples
+
+## Security Considerations
+
+- Never expose sensitive information in demos
+- Use placeholder data for examples
+- Validate all user inputs
+- Follow OWASP guidelines for web security
+- Document any intentional security simplifications for demo purposes
+
+## Workflow Efficiency Guidelines
+
+### Before Starting Major Changes
+1. **Check environment compatibility** (Node.js version, etc.)
+2. **Verify all dependencies exist** with correct versions
+3. **Locate configuration files** using absolute paths
+4. **Read files before editing** - always use Read tool first
+
+### Common File Locations
+- CI/CD workflows: `/workspace/.github/workflows/`
+- E2E tests: `/workspace/packages/e2e-tests/`
+- Documentation: `/workspace/docs/`
+- Types: `/workspace/packages/app/src/types/`
+
+### Tool Usage Best Practices
+1. **Batch related operations** - Use multiple tool calls in parallel when possible
+2. **Use Glob for finding files** - More efficient than multiple LS commands
+3. **Check command output** - Don't assume operations succeeded
+4. **Handle errors gracefully** - Have fallback plans for common issues
+
+### File System Operations
+
+#### Efficient Patterns
+1. **Bulk File Discovery**
+   ```bash
+   # Good - Single glob for multiple patterns
+   Glob("**/*.{test,spec}.{js,ts}")
+
+   # Avoid - Multiple sequential globs
+   Glob("**/*.test.js")
+   Glob("**/*.test.ts")
+   ```
+
+2. **Smart File Reading**
+   - Read configuration files early to understand project structure
+   - Use `head_limit` parameter in `Grep` for large codebases
+   - Read multiple related files in parallel when analyzing code patterns
+
+3. **Batch Editing**
+   - Group related changes together
+   - Use `replace_all` parameter when renaming variables/functions
+   - Plan multi-file refactoring before starting
+
+### Test Framework Migration Pattern
+
+1. **Initial Assessment Phase**
+   - Use `Glob` to find all test files at once
+   - Read package.json files to understand current dependencies
+   - Check CI workflows early to understand test execution context
+
+2. **Common Mistakes to Avoid**
+   - Creating files one by one instead of batch operations
+   - Incomplete initial implementation requiring multiple edits
+   - Missing configuration updates (tsconfig.json, CI workflows)
+   - Installing dependencies one by one instead of batch updates
+
+3. **Systematic Approach**
+   - Map old test structure to new framework
+   - Create all page objects first before migrating tests
+   - Update all related configuration files together
+   - Test locally before pushing changes
+
+### Monorepo-Specific Patterns
+
+1. **Workspace Management**
+   - Check workspace configuration files first (pnpm-workspace.yaml, etc.)
+   - Understand package interdependencies
+   - Use workspace-aware commands (`pnpm -w`, `pnpm -F <package>`)
+
+2. **Dependency Installation**
+   - Use correct package manager workspace commands
+   - Install at appropriate level (workspace root vs package)
+   - Verify lockfile updates after changes
+
+### CI/CD Best Practices
+
+1. **Proactive Checks**
+   - Always check existing CI workflows before making changes
+   - Verify workspace configurations (monorepo setup, package managers)
+   - Test locally mimicking CI environment when possible
+
+2. **Common CI Issues**
+   - Missing working directory specifications
+   - Incorrect dependency installation commands for monorepos
+   - Browser installation requirements for E2E tests
+   - Node.js version mismatches