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/config.rs

@@ -3,6 +3,7 @@ pub struct Config {
     pub host: String,
     pub port: u32,
     pub prefork: bool,
+    pub auth_secret: String,
 }
 
 impl Config {
@@ -15,6 +16,7 @@ impl Config {
                 .parse()
                 .expect("PORT is not a number"),
             prefork: std::env::var("PREFORK").is_ok_and(|v| v == "1"),
+            auth_secret: std::env::var("AUTH_SECRET").unwrap_or_else(|_| "secret".into()),
         }
     }