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/static/css/patterns.css

@@ -348,7 +348,6 @@
     background: none;
     border: none;
     color: var(--text-muted);
-    font-size: 0.9rem;
     cursor: pointer;
     padding: 2px 4px;
     border-radius: 4px;
@@ -356,6 +355,11 @@
     transition: color 0.2s, background 0.2s;
 }
 
+.pattern-rect-row .pattern-rect-remove-btn .icon {
+    width: 14px;
+    height: 14px;
+}
+
 .pattern-rect-row .pattern-rect-remove-btn:hover {
     color: var(--danger-color);
     background: rgba(244, 67, 54, 0.1);