Feat: Implement basic web authentication and UI

This commit introduces the foundation for web-based authentication and
user interface. It includes:

- **Session Management**: Securely handling user sessions using
  cryptographically generated tokens, cookies with appropriate security
  flags, and server-side storage.
- **Login/Logout Functionality**: Endpoints for users to log in with
  their credentials and log out, clearing their session.
- **User Interface**: Basic templates for the login page, a list of
  cases, and a detailed view of a single case, allowing users to
  navigate and view their data.
- **Authorization**: An `AuthenticatedWebUser` extractor to ensure only
  logged-in users can access protected web routes.
- **Configuration**: Added a `cookie_secure` option to the configuration
  to control the `Secure` flag on session cookies, useful for local
  development.
- **Dependencies**: Added necessary dependencies for password hashing,
  time handling, and TOML file manipulation.
- **Helper Binary**: Included a `hash-password` binary to simplify
  generating bcrypt hashes for user passwords.

server/src/error.rs

@@ -7,15 +7,26 @@ pub enum AppError {
     BadRequest(String),
     NotFound(String),
     Internal(String),
+    /// 302 redirect. Used by web auth to send unauthenticated users to login.
+    Redirect(String),
 }
 
 impl IntoResponse for AppError {
     fn into_response(self) -> Response {
+        if let Self::Redirect(url) = &self {
+            return Response::builder()
+                .status(StatusCode::FOUND)
+                .header(axum::http::header::LOCATION, url)
+                .body(axum::body::Body::empty())
+                .unwrap();
+        }
+
         let (status, message) = match &self {
             Self::Unauthorized => (StatusCode::UNAUTHORIZED, "Unauthorized".to_owned()),
             Self::BadRequest(msg) => (StatusCode::BAD_REQUEST, msg.clone()),
             Self::NotFound(msg) => (StatusCode::NOT_FOUND, msg.clone()),
             Self::Internal(msg) => (StatusCode::INTERNAL_SERVER_ERROR, msg.clone()),
+            Self::Redirect(_) => unreachable!(),
         };
 
         let body = axum::Json(json!({ "error": message }));