feat: add profile setup, verification, and authentication context

- Implement ProfileSetup component for user profile creation with username validation.
- Create ProtectedRoute component to guard routes based on authentication status.
- Add VerifyAuthCode component for email verification with resend functionality.
- Establish AuthContext for managing user authentication state and actions.
- Enhance CookieContext for consent management with server-side verification.
- Set up Firebase configuration for authentication and analytics.
- Update styles for authentication components and header layout.
- Configure Vite proxy for API requests during development.

backend/src/config/db.ts

@@ -9,6 +9,7 @@ const pool = mysql.createPool({
     password: process.env.DB_PASSWORD,
     database: process.env.DB_NAME,
     port: Number(process.env.DB_PORT) || 3306,
+    connectTimeout: Number(process.env.DB_CONNECT_TIMEOUT_MS) || 3500,
     waitForConnections: true,
     connectionLimit: 10,
     queueLimit: 0