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>

package.json

@@ -14,17 +14,22 @@
 		"format": "prettier --write .",
 		"test": "bunx --bun svelte-kit sync && bunx --bun vitest run",
 		"test:watch": "bunx --bun svelte-kit sync && bunx --bun vitest",
-		"test:coverage": "vitest run --coverage"
+		"test:coverage": "vitest run --coverage",
+		"test:e2e": "bunx playwright test",
+		"test:e2e:ui": "bunx playwright test --ui",
+		"test:e2e:debug": "bunx playwright test --debug"
 	},
 	"devDependencies": {
 		"@biomejs/biome": "^2.4.4",
 		"@eslint/js": "^10.0.1",
+		"@playwright/test": "^1.58.2",
 		"@sveltejs/adapter-node": "^5.5.3",
 		"@sveltejs/kit": "^2.50.2",
 		"@sveltejs/vite-plugin-svelte": "^6.2.4",
 		"@tailwindcss/vite": "^4.2.0",
 		"@vitest/coverage-v8": "^4.0.18",
 		"bun-types": "^1.3.9",
+		"dotenv": "^17.3.1",
 		"eslint": "^10.0.0",
 		"eslint-plugin-svelte": "^3.15.0",
 		"globals": "^17.3.0",