feat(auth): implement user registration and login with JWT authentication

- Added `bcrypt`, `jsonwebtoken`, and `once_cell` dependencies to manage password hashing and JWT handling.
- Created `Claims` struct for JWT claims and implemented token generation in the login route.
- Implemented user registration and authentication logic in the `auth` module.
- Updated error handling to include validation errors.
- Created new routes for user registration and login, and integrated them into the main router.
- Added tests for the authentication flow, including registration and login scenarios.
- Updated user model to include a password hash field.
- Refactored user creation logic to include password validation.
- Adjusted feed and user routes to utilize JWT for authentication.

thoughts-backend/.env

@@ -4,3 +4,4 @@ PORT=8000
 DATABASE_URL="postgresql://postgres:postgres@localhost/thoughts"
 #DATABASE_URL=postgres://thoughts_user:postgres@database:5432/thoughts_db
 PREFORK=0
+AUTH_SECRET=your_secret_key_here