Add CSPT entity, processed CSS source type, reverse filter, and UI improvements

- Add Color Strip Processing Template (CSPT) entity: reusable filter chains
  for 1D LED strip postprocessing (backend, storage, API, frontend CRUD)
- Add "processed" color strip source type that wraps another CSS source and
  applies a CSPT filter chain (dataclass, stream, schema, modal, cards)
- Add Reverse filter for strip LED order reversal
- Add CSPT and processed CSS nodes/edges to visual graph editor
- Add CSPT test preview WS endpoint with input source selection
- Add device settings CSPT template selector (add + edit modals with hints)
- Use icon grids for palette quantization preset selector in filter lists
- Use EntitySelect for template references and test modal source selectors
- Fix filters.css_filter_template.desc missing localization
- Fix icon grid cell height inequality (grid-auto-rows: 1fr)
- Rename "Processed" subtab to "Processing Templates"
- Localize all new strings (en/ru/zh)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/wled_controller/templates/modals/add-device.html

@@ -256,6 +256,16 @@
                         <option value="indicator">Indicator</option>
                     </select>
                 </div>
+                <div class="form-group" id="device-cspt-group">
+                    <div class="label-row">
+                        <label for="device-css-processing-template" data-i18n="device.css_processing_template">Strip Processing Template:</label>
+                        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
+                    </div>
+                    <small class="input-hint" style="display:none" data-i18n="device.css_processing_template.hint">Default processing template applied to all color strip outputs on this device</small>
+                    <select id="device-css-processing-template">
+                        <option value="">—</option>
+                    </select>
+                </div>
                 <div id="add-device-error" class="error-message" style="display: none;"></div>
             </form>
         </div>