feat: redesign media browser UI

- Root folder cards with hero-style layout and SVG icons
- Full-width thumbnails with aspect-ratio grid items
- List view column headers (Name, Bitrate, Duration, Size)
- Modernized breadcrumb with pill segments and overflow handling
- Proper skeleton shimmer replacing emoji hourglass on thumbnails
- Pagination shows "Showing X-Y of Z" item count
- Refined hover effects, animations, and visual hierarchy
- Download button revealed on row hover in list view
- Type badges hidden by default, shown on hover
- Localized new keys in en.json and ru.json

media_server/static/index.html

@@ -290,6 +290,7 @@
                     <span id="pageTotal">/ 1</span>
                 </div>
                 <button id="nextPage" onclick="nextPage()" data-i18n="browser.next">Next</button>
+                <span class="pagination-showing" id="paginationShowing"></span>
             </div>
         </div>