Add browser search/filter for media items

- Search bar appears when browsing inside a folder
- Client-side filtering with 200ms debounce
- Clear button and search icon
- Hides at root level, resets on navigation
- Localized placeholder (en/ru)

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

media_server/static/index.html

@@ -196,6 +196,13 @@
                         <span data-i18n="browser.play_all">Play All</span>
                     </button>
                 </div>
+                <div class="browser-search-wrapper" id="browserSearchWrapper" style="display: none;">
+                    <svg class="browser-search-icon" viewBox="0 0 24 24" width="16" height="16"><path fill="currentColor" d="M15.5 14h-.79l-.28-.27A6.471 6.471 0 0016 9.5 6.5 6.5 0 109.5 16c1.61 0 3.09-.59 4.23-1.57l.27.28v.79l5 4.99L20.49 19l-4.99-5zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"/></svg>
+                    <input type="text" id="browserSearchInput" class="browser-search-input" data-i18n-placeholder="browser.search" placeholder="Search..." oninput="onBrowserSearch()">
+                    <button class="browser-search-clear" id="browserSearchClear" onclick="clearBrowserSearch()" style="display: none;">
+                        <svg viewBox="0 0 24 24" width="14" height="14"><path fill="currentColor" d="M19 6.41L17.59 5 12 10.59 6.41 5 5 6.41 10.59 12 5 17.59 6.41 19 12 13.41 17.59 19 19 17.59 13.41 12z"/></svg>
+                    </button>
+                </div>
                 <div class="browser-toolbar-right">
                     <label class="items-per-page-label">
                         <span data-i18n="browser.items_per_page">Items per page:</span>