Add media browser with grid/compact/list views and single-click playback

- Add browser UI with three view modes (grid, compact, list) and pagination
- Add file browsing, thumbnail loading, download, and play endpoints
- Add duration extraction via mutagen for media files
- Single-click plays media or navigates folders, with play overlay on hover
- Add type badges, file size display, and duration metadata
- Add localization keys for browser UI (en/ru)

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

media_server/static/locales/en.json

@@ -115,8 +115,14 @@
   "browser.select_folder_option": "Select a folder...",
   "browser.no_folder_selected": "Select a folder to browse media files",
   "browser.no_items": "No media files found in this folder",
+  "browser.view_grid": "Grid view",
+  "browser.view_compact": "Compact view",
+  "browser.view_list": "List view",
+  "browser.items_per_page": "Items per page:",
+  "browser.page": "Page",
   "browser.previous": "Previous",
   "browser.next": "Next",
+  "browser.download": "Download",
   "browser.play_success": "Playing {filename}",
   "browser.play_error": "Failed to play file",
   "browser.error_loading": "Error loading directory",