Add media browser feature with UI improvements

- Refactored index.html: Split into separate HTML (309 lines), CSS (908 lines), and JS (1,286 lines) files
- Implemented media browser with folder configuration, recursive navigation, and thumbnail display
- Added metadata extraction using mutagen library (title, artist, album, duration, bitrate, codec)
- Implemented thumbnail generation and caching with SHA256 hash-based keys and LRU eviction
- Added platform-specific file playback (os.startfile on Windows, xdg-open on Linux, open on macOS)
- Implemented path validation security to prevent directory traversal attacks
- Added smooth thumbnail loading with fade-in animation and loading spinner
- Added i18n support for browser (English and Russian)
- Updated dependencies: mutagen>=1.47.0, pillow>=10.0.0
- Added comprehensive media browser documentation to README

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

media_server/services/windows_media.py

@@ -666,3 +666,24 @@ class WindowsMediaController(MediaController):
         except Exception as e:
             logger.error(f"Failed to seek: {e}")
             return False
+
+    async def open_file(self, file_path: str) -> bool:
+        """Open a media file with the default system player (Windows).
+
+        Uses os.startfile() to open the file with the default application.
+
+        Args:
+            file_path: Absolute path to the media file
+
+        Returns:
+            True if successful, False otherwise
+        """
+        try:
+            import os
+            loop = asyncio.get_event_loop()
+            await loop.run_in_executor(None, lambda: os.startfile(file_path))
+            logger.info(f"Opened file with default player: {file_path}")
+            return True
+        except Exception as e:
+            logger.error(f"Failed to open file {file_path}: {e}")
+            return False