Add Play All, home navigation, and UI improvements

- Add Play All button with M3U playlist generation (local temp file with absolute paths)
- Replace folder combobox with root folder cards and home icon breadcrumb
- Fix compact grid card sizing (64x64 thumbnails, align-items: start)
- Add loading spinner when browsing folders
- Cache browse items to avoid re-fetching on view mode switch
- Remove unused browser-controls CSS
- Add localization keys for Play All and Home (en/ru)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

media_server/static/locales/en.json

@@ -110,6 +110,7 @@
   "callbacks.confirm.delete": "Are you sure you want to delete the callback \"{name}\"?",
   "callbacks.confirm.unsaved": "You have unsaved changes. Are you sure you want to discard them?",
   "browser.title": "Media Browser",
+  "browser.home": "Home",
   "browser.manage_folders": "Manage Folders",
   "browser.select_folder": "Select a folder...",
   "browser.select_folder_option": "Select a folder...",
@@ -125,6 +126,9 @@
   "browser.download": "Download",
   "browser.play_success": "Playing {filename}",
   "browser.play_error": "Failed to play file",
+  "browser.play_all": "Play All",
+  "browser.play_all_success": "Playing {count} files",
+  "browser.play_all_error": "Failed to play folder",
   "browser.error_loading": "Error loading directory",
   "browser.error_loading_folders": "Failed to load media folders",
   "browser.manage_folders_hint": "Folder management coming soon! For now, edit config.yaml to add media folders.",