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>

core/internal/server/router.go

@@ -21,6 +21,7 @@ import (
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/network"
 	serverPlugins "github.com/AvengeMedia/DankMaterialShell/core/internal/server/plugins"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/sysupdate"
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/tailscale"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/thememode"
 	serverThemes "github.com/AvengeMedia/DankMaterialShell/core/internal/server/themes"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/wayland"
@@ -110,6 +111,15 @@ func RouteRequest(conn net.Conn, req models.Request) {
 		return
 	}
 
+	if strings.HasPrefix(req.Method, "tailscale.") {
+		if tailscaleManager == nil {
+			models.RespondError(conn, req.ID, "Tailscale not available")
+			return
+		}
+		tailscale.HandleRequest(conn, req, tailscaleManager)
+		return
+	}
+
 	if strings.HasPrefix(req.Method, "dwl.") {
 		if dwlManager == nil {
 			models.RespondError(conn, req.ID, "dwl manager not initialized")