fix(alerts): harden with security fixes, design compliance, and test coverage (#570)

* fix(alerts): harden with security fixes, design compliance, and test coverage

Add authMiddleware to all alert endpoints, validate notification test
dispatch inputs, fix restart_count metric via Docker inspect, correct
network metric units, replace any types with DockerContainerStats
interface, add webhook timeouts and dispatch error tracking.

Frontend: migrate Select to Combobox, add ScrollArea and delete
confirmation AlertDialog, fix icon strokeWidth to 1.5.

Add update availability notifications for both Sencho version updates
(6-hour check in MonitorService) and stack image updates (state
transition detection in ImageUpdateService). Extract shared version
fetch logic into utils/version-check.ts.

Add diagnostic logging gated behind developer_mode for MonitorService
breach state machine and NotificationService dispatch routing.

Tests: 24 new alert API integration tests, restart_count and version
check unit tests (688 total passing). Docs updated with HTTPS
requirement, update notifications section, and troubleshooting guide.

* fix(alerts): remove unused TEST_USERNAME import in alerts-api tests

backend/src/services/DockerController.ts

@@ -1028,6 +1028,13 @@ class DockerController {
     return typeof stats === 'string' ? stats : JSON.stringify(stats);
   }
 
+  /** Return the cumulative restart count for a container via inspect(). */
+  public async getContainerRestartCount(containerId: string): Promise<number> {
+    const container = this.docker.getContainer(containerId);
+    const info = await container.inspect();
+    return info.RestartCount ?? 0;
+  }
+
   /**
    * Exec into a container with full session isolation.
    * All state (exec instance, stream) lives in this closure - no singleton traps.