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/tsconfig.json

@@ -1,7 +1,4 @@
 {
 	"extends": "../../tsconfig.json",
-	"compilerOptions": {
-		"types": ["bun-types"]
-	},
 	"include": ["src"]
 }