feat(backend): add BetterAuth email/password authentication

- Add PostgreSQL connection (src/db.ts)
- Configure BetterAuth with email/password (src/auth/index.ts)
- Add session middleware for route protection (src/auth/session-middleware.ts)
- Add registerAuthHandlers for mounting auth routes (src/auth/http.ts)
- Rename index.ts to server.ts
- Add .env.example with required environment variables

Co-authored-by: Ona <no-reply@ona.com>

apps/aris-backend/src/db.ts

@@ -0,0 +1,5 @@
+import { Pool } from "pg"
+
+export const pool = new Pool({
+	connectionString: process.env.DATABASE_URL,
+})