feat: add iCalendar demo feature

[eins78]

Implements a minimal iCalendar demo feature for testing calendar client compatibility.

Closes #296

See issue for implementation details.

[eins78]

CI Status Update:

• ✅ Build & Lint: Passing
• ✅ Docker Build: Passing
• ❌ E2E Tests: Failing due to Cypress binary installation issue in CI (not related to code changes)

The E2E test failure is due to a CI infrastructure issue where the Cypress binary is not being properly cached/installed. The error message indicates:

Error: The cypress npm package is installed, but the Cypress binary is missing.
We expected the binary to be installed here: /home/runner/.cache/Cypress/14.2.1/Cypress/Cypress

All code changes have been validated and formatting/linting issues have been resolved. The code is ready for review.

[Copilot]

Pull Request Overview

This PR implements a comprehensive iCalendar demo feature for testing calendar client compatibility. The implementation follows RFC 5545 specifications while including vendor-specific workarounds for real-world client behavior.

Key changes include:

• API endpoint for generating dynamic iCalendar feeds with event cancellation support
• Interactive demo page with form-based feed generation and testing instructions
• Comprehensive unit tests and detailed documentation covering client compatibility

Reviewed Changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/app/src/views/Home.ts	Adds navigation link to the new iCalendar demo
packages/app/src/utils/ical-helpers.ts	Core utility functions for parsing parameters and adding vendor extensions
packages/app/src/utils/ical-helpers.test.ts	Comprehensive unit tests for the helper functions
packages/app/src/types/events.ts	Type definitions for event data structures and iCalendar options
packages/app/src/routes/demos/ical.ts	Demo page with interactive form and client testing instructions
packages/app/src/routes/api/ical.ts	API endpoint for generating iCalendar feeds
packages/app/src/app.ts	Router configuration for new demo and API routes
packages/app/package.json	Dependencies for iCalendar generation and testing
docs/features/ical.md	Comprehensive feature documentation with client compatibility details
CLAUDE.md	Updates to git workflow guidelines for commit squashing
AGENTS.md	New AI agent guidelines for development standards
.devcontainer/init-firewall.sh	Firewall configuration update

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

[Copilot]

[nitpick] Consider extracting the magic number 0 into a named constant like MIN_DURATION_MINUTES for better maintainability and clarity.

Suggested change

	if (isNaN(durationMin) || durationMin <= 0) {
	if (isNaN(durationMin) || durationMin <= MIN_DURATION_MINUTES) {

[Copilot]

[nitpick] The magic number 60000 (milliseconds in a minute) should be extracted into a named constant like MILLISECONDS_PER_MINUTE for better readability.

Suggested change

	const endDate = new Date(startDate.getTime() + durationMin * 60000);
	const endDate = new Date(startDate.getTime() + durationMin * MILLISECONDS_PER_MINUTE);

[Copilot]

document.execCommand('copy') is deprecated. Use the modern Clipboard API (navigator.clipboard.writeText()) with fallback for better browser compatibility.

Suggested change

	document.getElementById("copy-btn").addEventListener("click", () => {
	const input = document.getElementById("feed-url");
	input.select();
	document.execCommand("copy");
	const btn = document.getElementById("copy-btn");
	const originalText = btn.textContent;
	btn.textContent = "Copied!";
	setTimeout(() => (btn.textContent = originalText), 2000);
	document.getElementById("copy-btn").addEventListener("click", async () => {
	const input = document.getElementById("feed-url");
	input.select();
	try {
	if (navigator.clipboard && navigator.clipboard.writeText) {
	await navigator.clipboard.writeText(input.value);
	} else {
	document.execCommand("copy"); // Fallback for older browsers
	}
	const btn = document.getElementById("copy-btn");
	const originalText = btn.textContent;
	btn.textContent = "Copied!";
	setTimeout(() => (btn.textContent = originalText), 2000);
	} catch (err) {
	console.error("Failed to copy text: ", err);
	}