feat(FN-2976): detect and display external Tailscale funnel tunnels in remo

Merges external Tailscale funnel detection (FN-2976) — adds types, detection logic, status inclusion, kill flow, and a dedicated UI panel for funnel processes started outside Fusion — alongside custom AI providers API routes and a new settings UI section (FN-2965).

Fusion-Task-Id: FN-2976

packages/dashboard/app/api/legacy.ts

@@ -473,6 +473,10 @@ export interface RemoteStatus {
   lastError: string | null;
   lastErrorCode?: string | null;
   cloudflaredAvailable?: boolean | null;
+  externalTunnel?: {
+    provider: "tailscale" | "cloudflare";
+    url: string | null;
+  } | null;
   restore?: {
     outcome: "applied" | "skipped" | "failed";
     reason: string;
@@ -525,6 +529,12 @@ export function stopRemoteTunnel(projectId?: string): Promise<{ state: "stopped"
   });
 }
 
+export function killExternalTunnel(projectId?: string): Promise<{ ok: boolean }> {
+  return api<{ ok: boolean }>(withProjectId("/remote/tunnel/kill-external", projectId), {
+    method: "POST",
+  });
+}
+
 export function regenerateRemotePersistentToken(projectId?: string): Promise<{ token: string; maskedToken: string }> {
   return api<{ token: string; maskedToken: string }>(withProjectId("/remote/token/persistent/regenerate", projectId), {
     method: "POST",