Add Playwright e2e coverage + comment-level video upload workflow (#40)

## Summary
- add Playwright e2e auth setup + seeded test DB flow
- fix Playwright startup order so DB seed runs before web server uses SQLite
- add full trip-planning e2e scenario (future trip, travellers, destination, flight, lodging, upcoming verification)
- configure Auth.js custom sign-in page for base-path routing
- add repo guidance in AGENTS.md / CLAUDE.md requiring e2e for user-facing changes
- document and validate comment-level Gitea video attachment workflow (create comment, upload to comment assets endpoint)

## Validation
- bunx playwright test e2e/auth.test.ts --project=chromium\n- bunx playwright test e2e/trip-planning.test.ts --project=chromium
- PW_VIDEO_MODE=on PW_TRACE_MODE=off bunx playwright test e2e/trip-planning.test.ts --project=chromium

## Issue
- relates to #38

Co-authored-by: AI Agent <ai-agent@campbellwireless.net>
Reviewed-on: #40
Co-authored-by: Shaun Campbell <shaun@campbellwireless.net>
Co-committed-by: Shaun Campbell <shaun@campbellwireless.net>

e2e/setup/test-users.ts

@@ -0,0 +1,15 @@
+// Shared test user definitions — no runtime deps, importable from both Node and Bun contexts.
+export const TEST_USERS = {
+	regular: {
+		username: 'e2e_user',
+		fullName: 'E2E Regular User',
+		email: 'e2e_user@test.local',
+		password: 'e2e-regular-password123'
+	},
+	admin: {
+		username: 'e2e_admin',
+		fullName: 'E2E Admin User',
+		email: 'e2e_admin@test.local',
+		password: 'e2e-admin-password123'
+	}
+} as const;