refactor: key colors targets → CSS source type, HA target improvements

Key Colors refactor:
- New `key_colors` CSS source type with inline rectangles
- KeyColorsColorStripStream: extracts N colors from screen regions
- CSS editor: EntitySelect for picture source, IconSelect for color mode
- Configure Regions button on card opens pattern canvas editor
- Live WS preview at 5 FPS with rectangle overlay + color swatches
- Removed KC target type, pattern template entity, and related API routes
- Removed KC/pattern template sections from Targets tab

HA light target improvements:
- Update rate, transition, mappings, brightness VS now editable via PUT
- Card crosslinks for HA source, CSS source, brightness VS
- HA connection status icon, text metrics (Hz, uptime)
- Brightness value source selector in editor

server/src/wled_controller/templates/modals/ha-light-editor.html

@@ -64,14 +64,27 @@
                         oninput="document.getElementById('ha-light-editor-transition-display').textContent = parseFloat(this.value).toFixed(1)">
                 </div>
 
+                <!-- Brightness Value Source -->
+                <div class="form-group">
+                    <div class="label-row">
+                        <label for="ha-light-editor-brightness-vs" data-i18n="targets.brightness_vs">Brightness Source:</label>
+                    </div>
+                    <select id="ha-light-editor-brightness-vs">
+                        <option value="">None</option>
+                    </select>
+                </div>
+
                 <!-- Light Mappings -->
                 <div class="form-group">
                     <div class="label-row">
                         <label data-i18n="ha_light.mappings">Light Mappings:</label>
-                        <button type="button" class="btn btn-sm btn-secondary" onclick="addHALightMapping()" data-i18n-title="ha_light.mappings.add">+</button>
+                        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?" data-i18n-aria-label="aria.hint">?</button>
                     </div>
-                    <small class="input-hint" data-i18n="ha_light.mappings.hint">Map LED ranges to HA light entities. Each mapping averages the LED segment to a single color.</small>
+                    <small class="input-hint" style="display:none" data-i18n="ha_light.mappings.hint">Map LED ranges to HA light entities. Each mapping averages the LED segment to a single color.</small>
                     <div id="ha-light-mappings-list"></div>
+                    <button type="button" class="btn btn-sm btn-secondary" onclick="addHALightMapping()" style="margin-top: 4px;">
+                        + <span data-i18n="ha_light.mappings.add">Add Mapping</span>
+                    </button>
                 </div>
 
                 <!-- Description -->