frontend: add login page and auth guard

Add authentication flow to the frontend:
- authStore with token management (localStorage persistence)
- Login page with username/password form at /login
- Layout-level auth guard that redirects to /login when no valid
  session exists, validates token on load via GET /api/auth/me
- Top navigation bar showing username and admin link when applicable

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gamestream-webtransport-proxy/src/apps.rs

@@ -47,7 +47,16 @@ struct GetAppsResponse {
 impl crate::backend::Backend {
     #[craft(endpoint(status_codes(StatusCode::OK, StatusCode::INTERNAL_SERVER_ERROR)))]
     pub async fn get_apps(self: ::std::sync::Arc<Self>, depot: &mut Depot) -> AppResult<Json<GetAppsResponse>> {
-        let user = auth::get_user_from_depot(depot).cloned();
+        let user = match auth::get_user_from_depot(depot) {
+            Some(u) => u.clone(),
+            None => {
+                error!("get_apps reached without authenticated user in depot");
+                return Err(AppError {
+                    status_code: StatusCode::UNAUTHORIZED,
+                    description: "Not authenticated".to_string(),
+                });
+            }
+        };
         let standard_error = Err(AppError {
             status_code: StatusCode::INTERNAL_SERVER_ERROR,
             description: "failed to get available apps".to_string(),
@@ -146,18 +155,16 @@ impl crate::backend::Backend {
         }
 
         // Filter apps by user permissions (admins see everything)
-        if let Some(ref user) = user {
-            if !user.is_admin {
-                let permissions = self.db.get_permissions(&user.id).unwrap_or_default();
-                for (server_name, apps) in get_apps_resp.apps.iter_mut() {
-                    apps.retain(|app| {
-                        permissions.iter().any(|p| {
-                            p.server == *server_name && p.app_id == app.id as i64
-                        })
-                    });
-                }
-                get_apps_resp.apps.retain(|_, apps| !apps.is_empty());
+        if !user.is_admin {
+            let permissions = self.db.get_permissions(&user.id).unwrap_or_default();
+            for (server_name, apps) in get_apps_resp.apps.iter_mut() {
+                apps.retain(|app| {
+                    permissions.iter().any(|p| {
+                        p.server == *server_name && p.app_id == app.id as i64
+                    })
+                });
             }
+            get_apps_resp.apps.retain(|_, apps| !apps.is_empty());
         }
 
         Ok(Json(get_apps_resp))

gamestream-webtransport-proxy/src/proxy/handler.rs

@@ -85,31 +85,17 @@ impl crate::proxy::Proxy {
             description: "Could not start stream".to_string(),
         });
 
-        // Validate single-use stream token
+        // Validate single-use stream token via the shared helper so this
+        // handler and its unit tests exercise the same code path.
         let provided_token = req.query::<String>("token").unwrap_or_default();
-        {
-            let mut token_guard = self.stream_token.write().await;
-            match token_guard.take() {
-                Some(expected) if expected == provided_token => {
-                    // Token consumed successfully (single-use)
-                    info!("Stream token validated and consumed");
-                }
-                Some(_) => {
-                    error!("Invalid stream token provided");
-                    return Err(AppError {
-                        status_code: StatusCode::UNAUTHORIZED,
-                        description: "Invalid stream token".to_string(),
-                    });
-                }
-                None => {
-                    error!("Stream token already consumed");
-                    return Err(AppError {
-                        status_code: StatusCode::UNAUTHORIZED,
-                        description: "Stream token already used".to_string(),
-                    });
-                }
-            }
+        if let Err(msg) = super::validate_stream_token(&self, &provided_token).await {
+            error!("Stream token validation failed: {msg}");
+            return Err(AppError {
+                status_code: StatusCode::UNAUTHORIZED,
+                description: msg,
+            });
         }
+        info!("Stream token validated and consumed");
 
         info!("WebTransport connection initiated");
         let (wt_stream_send, wt_stream_recv, wt_datagram_send) = match setup_webtransport(req).await

gamestream-webtransport-proxy/src/proxy/mod.rs

@@ -85,8 +85,9 @@ pub async fn validate_stream_token(proxy: &Proxy, provided: &str) -> std::result
     match token_guard.take() {
         Some(expected) if expected == provided => Ok(()),
         Some(_) => {
-            // Put the token back since it wasn't matched
-            // Actually no — the design is that any attempt consumes it for security
+            // Wrong token: still consumed by the `take()` above. Any validation
+            // attempt — correct or not — invalidates the token, so a wrong
+            // guess cannot be followed by a correct one.
             Err("Invalid stream token".to_string())
         }
         None => Err("Stream token already used".to_string()),

gamestream-webtransport-proxy/src/stream.rs

@@ -90,20 +90,28 @@ impl crate::backend::Backend {
         });
 
         // Check app permission
-        if let Some(user) = auth::get_user_from_depot(depot) {
-            if !user.is_admin {
-                match self.db.check_app_permission(&user.id, &body.server, body.id as i64) {
-                    Ok(true) => {}
-                    Ok(false) => {
-                        return Err(AppError {
-                            status_code: StatusCode::FORBIDDEN,
-                            description: "You do not have permission to access this application".to_string(),
-                        });
-                    }
-                    Err(e) => {
-                        error!("Permission check error: {e}");
-                        return standard_error;
-                    }
+        let user = match auth::get_user_from_depot(depot) {
+            Some(u) => u.clone(),
+            None => {
+                error!("post_stream_start reached without authenticated user in depot");
+                return Err(AppError {
+                    status_code: StatusCode::UNAUTHORIZED,
+                    description: "Not authenticated".to_string(),
+                });
+            }
+        };
+        if !user.is_admin {
+            match self.db.check_app_permission(&user.id, &body.server, body.id as i64) {
+                Ok(true) => {}
+                Ok(false) => {
+                    return Err(AppError {
+                        status_code: StatusCode::FORBIDDEN,
+                        description: "You do not have permission to access this application".to_string(),
+                    });
+                }
+                Err(e) => {
+                    error!("Permission check error: {e}");
+                    return standard_error;
                 }
             }
         }