feat(tailscale): add Tailscale control center widget (#1875)

* feat(tailscale): add Tailscale control center widget

Full-stack Tailscale integration for DMS control center:

Backend (Go):
- Event-driven manager via WatchIPNBus (no polling)
- Reconnects with exponential backoff when tailscaled unavailable
- Typed conversion from ipnstate.Status to QML-friendly IPC types
- Testable via tailscaleClient interface with mock watcher
- Manager cleanup in cleanupManagers()
- 19 unit tests

Frontend (QML):
- TailscaleService with WebSocket subscription
- TailscaleWidget with peer list, filter chips, search
- Copy-to-clipboard for IPs and DNS names
- Daemon lifecycle handling (offline/stopped states)

Dependencies:
- Add tailscale.com v1.96.1 (official local API client)
- Bump Go to 1.26.1 (required by tailscale.com)

* cleanups

---------

Co-authored-by: bbedward <bbedward@gmail.com>

quickshell/Services/DMSService.qml

@@ -64,6 +64,7 @@ Singleton {
     signal clipboardStateUpdate(var data)
     signal locationStateUpdate(var data)
     signal sysupdateStateUpdate(var data)
+    signal tailscaleStateUpdate(var data)
 
     property bool capsLockState: false
     property bool screensaverInhibited: false
@@ -398,6 +399,8 @@ Singleton {
             locationStateUpdate(data);
         } else if (service === "sysupdate") {
             sysupdateStateUpdate(data);
+        } else if (service === "tailscale") {
+            tailscaleStateUpdate(data);
         }
     }