fix: accurate port banner and tkinter graceful fallback

- Move startup banner into main.py so it shows the actual configured
  port instead of a hardcoded 8080 in the launcher scripts
- Wrap tkinter import in try/except so embedded Python (which lacks
  tkinter) logs a warning instead of crashing the overlay thread

server/src/wled_controller/core/capture/screen_overlay.py

@@ -278,7 +278,12 @@ class OverlayManager:
 
     def _start_tk_thread(self) -> None:
         def _run():
-            import tkinter as tk  # lazy import — tkinter unavailable in headless CI
+            try:
+                import tkinter as tk  # lazy import — tkinter unavailable in embedded Python / headless CI
+            except ImportError:
+                logger.warning("tkinter not available — screen overlay disabled")
+                self._tk_ready.set()
+                return
 
             try:
                 self._tk_root = tk.Tk()