feat(FN-2585): remove top-level remote access toggle

- Remove the standalone remoteEnabled setting from CLI, core settings defaults/types, and dashboard settings APIs/UI
- Treat remote access as enabled when an active provider is selected and that provider is configured as enabled
- Update remote auth and engine lifecycle checks to gate on provider activation instead of a global flag
- Adjust tests and add a changeset documenting the remote access configuration simplification

packages/dashboard/app/api/legacy.ts

@@ -404,7 +404,6 @@ export function updateSettings(settings: Partial<Settings>, projectId?: string):
 }
 
 export interface RemoteSettings {
-  remoteEnabled: boolean;
   remoteActiveProvider: "tailscale" | "cloudflare" | null;
   remoteTailscaleEnabled: boolean;
   remoteTailscaleHostname: string;