Add tags to all entity types with chip-based input and autocomplete

- Add `tags: List[str]` field to all 13 entity types (devices, output targets,
  CSS sources, picture sources, audio sources, value sources, sync clocks,
  automations, scene presets, capture/audio/PP/pattern templates)
- Update all stores, schemas, and route handlers for tag CRUD
- Add GET /api/v1/tags endpoint aggregating unique tags across all stores
- Create TagInput component with chip display, autocomplete dropdown,
  keyboard navigation, and API-backed suggestions
- Display tag chips on all entity cards (searchable via existing text filter)
- Add tag input to all 14 editor modals with dirty check support
- Add CSS styles and i18n keys (en/ru/zh) for tag UI
- Also includes code review fixes: thread safety, perf, store dedup

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

server/src/wled_controller/templates/modals/css-editor.html

@@ -576,6 +576,15 @@
                     </select>
                 </div>
 
+                <div class="form-group">
+                    <div class="label-row">
+                        <label data-i18n="tags.label">Tags:</label>
+                        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
+                    </div>
+                    <small class="input-hint" style="display:none" data-i18n="tags.hint">Assign tags for grouping and filtering cards</small>
+                    <div id="css-tags-container"></div>
+                </div>
+
                 <div id="css-editor-error" class="error-message" style="display: none;"></div>
             </form>
         </div>