feat: add BetterAuth authentication

- Add better-auth to backend and frontend
- Create auth tables (users, sessions, accounts, verifications)
- Mount BetterAuth handler on /api/auth/*
- Protect GET /api/tasks with session auth
- Add login page with email/password
- Add invite route for creating users
- Add logout button to header
- Cross-subdomain cookies for .donovankelly.xyz
- Fix page title to 'Hammer Queue'
- Keep bearer token for admin mutations (separate from session auth)
- Update docker-compose with BETTER_AUTH_SECRET and COOKIE_DOMAIN

backend/package.json

@@ -10,9 +10,10 @@
     "db:studio": "drizzle-kit studio"
   },
   "dependencies": {
+    "@elysiajs/cors": "^1.2.0",
+    "better-auth": "^1.4.17",
     "drizzle-orm": "^0.44.2",
     "elysia": "^1.2.25",
-    "@elysiajs/cors": "^1.2.0",
     "postgres": "^3.4.5"
   },
   "devDependencies": {