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/global-setup.ts

@@ -0,0 +1,20 @@
+import type { FullConfig } from '@playwright/test';
+import { spawnSync } from 'child_process';
+import { resolve } from 'path';
+import { config as dotenvConfig } from 'dotenv';
+
+dotenvConfig({ path: resolve(process.cwd(), '.env.test'), override: true });
+
+async function globalSetup(_config: FullConfig): Promise<void> {
+	console.log('[e2e] Seeding test database via Bun...');
+	const result = spawnSync('bun', ['run', 'e2e/setup/seed-db.ts'], {
+		env: { ...process.env },
+		stdio: 'inherit',
+		cwd: process.cwd()
+	});
+	if (result.status !== 0) {
+		throw new Error(`[e2e] DB seed script failed with exit code ${result.status}`);
+	}
+}
+
+export default globalSetup;