test(e2e): Remove LocalStack project from Playwright configuration

Remove the chromium-localstack project configuration as part of transitioning
from LocalStack E2E testing to real AWS testing.

LocalStack is an AWS service emulator for backend integration testing and
cannot support browser-based E2E tests of React frontend navigation. The
tests now run against real AWS using the standard chromium project.

Changes:
- Removed chromium-localstack project configuration (lines 71-79)
- All E2E tests now use chromium project with real AWS integration
- Completes LocalStack removal initiated in previous commit

References:
- /tmp/LOCALSTACK_WEEK1_FINAL_STATUS.md - Decision rationale
- /tmp/LOCALSTACK_RESEARCH_FINDINGS.md - Technical research

Author: scttfrdmn

cmd/prism-gui/frontend/playwright.config.js

@@ -66,16 +66,6 @@ export default defineConfig({
     {
       name: 'webkit',
       use: { ...devices['Desktop Safari'] },
-    },
-
-    // LocalStack testing project
-    {
-      name: 'chromium-localstack',
-      use: {
-        ...devices['Desktop Chrome'],
-      },
-      testMatch: /.*\.spec\.ts/,
-      grep: /@localstack/, // Only run tests tagged with @localstack
     }
   ],