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>

src/auth.ts

@@ -47,6 +47,9 @@ export const { handle, signIn, signOut } = SvelteKitAuth({
 		})
 	],
 	trustHost: true,
+	pages: {
+		signIn: '/trips/login'
+	},
 	callbacks: {
 		jwt({ token, profile, user }) {
 			const details = profile as
@@ -56,7 +59,7 @@ export const { handle, signIn, signOut } = SvelteKitAuth({
 						email?: string;
 						username?: string;
 						preferred_username?: string;
-					}
+				  }
 				| undefined;
 			if (details?.sub) {
 				token.sub = details.sub as string;