perf(daemon): skip the UI-thread datadir lock wait

Starting the daemon polls for an already-running node holding the
datadir, sleeping up to three 100 ms intervals to let a shutting-down
node clear out. When a start runs on the UI thread, that is up to 300 ms
of blocking sleep on the render thread.

- The lock-wait poll count is now a parameter. A start invoked on the UI
  thread passes 0, which does a single check and never sleeps; every
  other caller keeps the three-poll wait. The default is unchanged, so
  background starts behave exactly as before.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/daemon/daemon_controller.h

@@ -95,7 +95,7 @@ public:
     void setStateCallback(StateCallback callback);
     void syncSettings(const config::Settings* settings);
 
-    bool start(const config::Settings* settings);
+    bool start(const config::Settings* settings, int lockWaitPolls = 3);
     void stop(int waitMs);
     void markStopRequested();