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/app/src/error/user.rs

@@ -5,6 +5,7 @@ pub enum UserError {
     Forbidden,
     UsernameTaken,
     AlreadyFollowing,
+    Validation(String), // Added Validation variant
     Internal(String),
 }
 
@@ -16,6 +17,7 @@ impl std::fmt::Display for UserError {
             UserError::Forbidden => write!(f, "You do not have permission to perform this action"),
             UserError::UsernameTaken => write!(f, "Username is already taken"),
             UserError::AlreadyFollowing => write!(f, "You are already following this user"),
+            UserError::Validation(msg) => write!(f, "Validation error: {}", msg),
             UserError::Internal(msg) => write!(f, "Internal server error: {}", msg),
         }
     }