Update Web UI: Add server management scripts and improve UX

UI improvements:
- Add icon-based Execute/Edit/Delete buttons for scripts and callbacks
- Add execution result dialog with stdout/stderr and execution time
- Add favicon with media player icon
- Disable background scrolling when dialogs are open
- Add footer with author information and source code link

Backend enhancements:
- Add execution time tracking to script and callback execution
- Add /api/callbacks/execute endpoint for debugging callbacks
- Return detailed execution results (stdout, stderr, exit_code, execution_time)

Server management:
- Add scripts/start-server.bat - Start server with console window
- Add scripts/start-server-background.vbs - Start server silently
- Add scripts/stop-server.bat - Stop running server instances
- Add scripts/restart-server.bat - Restart the server

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

scripts/stop-server.bat

@@ -0,0 +1,19 @@
+@echo off
+REM Media Server Stop Script
+REM This script stops the running media server
+
+echo Stopping Media Server...
+echo.
+
+REM Find and kill Python processes running media_server.main
+for /f "tokens=2" %%i in ('tasklist /FI "IMAGENAME eq python.exe" /FO LIST ^| findstr /B "PID:"') do (
+    wmic process where "ProcessId=%%i" get CommandLine 2>nul | findstr /C:"media_server.main" >nul
+    if not errorlevel 1 (
+        taskkill /PID %%i /F
+        echo Media server process (PID %%i) terminated.
+    )
+)
+
+echo.
+echo Done! Media server stopped.
+pause