Add per-layer brightness source to composite CSS and enhance selectors

- Add optional brightness_source_id per composite layer using ValueStreamManager
- Use EntitySelect for composite layer source and brightness dropdowns
- Use IconSelect for composite blend mode and notification filter mode
- Add i18n keys for blend mode and filter mode descriptions (en/ru/zh)

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

server/src/wled_controller/static/locales/zh.json

@@ -902,6 +902,9 @@
   "color_strip.notification.filter_mode.off": "关闭",
   "color_strip.notification.filter_mode.whitelist": "白名单",
   "color_strip.notification.filter_mode.blacklist": "黑名单",
+  "color_strip.notification.filter_mode.off.desc": "接受所有通知",
+  "color_strip.notification.filter_mode.whitelist.desc": "仅列出的应用",
+  "color_strip.notification.filter_mode.blacklist.desc": "排除列出的应用",
   "color_strip.notification.filter_list": "应用列表：",
   "color_strip.notification.filter_list.hint": "每行一个应用名称。使用「浏览」从运行中的进程中选择。",
   "color_strip.notification.filter_list.placeholder": "Discord\nSlack\nTelegram",
@@ -945,10 +948,16 @@
   "color_strip.composite.source": "源",
   "color_strip.composite.blend_mode": "混合",
   "color_strip.composite.blend_mode.normal": "正常",
+  "color_strip.composite.blend_mode.normal.desc": "标准 Alpha 混合",
   "color_strip.composite.blend_mode.add": "叠加",
+  "color_strip.composite.blend_mode.add.desc": "通过叠加颜色提亮",
   "color_strip.composite.blend_mode.multiply": "正片叠底",
+  "color_strip.composite.blend_mode.multiply.desc": "通过相乘颜色变暗",
   "color_strip.composite.blend_mode.screen": "滤色",
+  "color_strip.composite.blend_mode.screen.desc": "提亮，正片叠底的反转",
   "color_strip.composite.opacity": "不透明度",
+  "color_strip.composite.brightness": "亮度",
+  "color_strip.composite.brightness.none": "— 无 —",
   "color_strip.composite.enabled": "启用",
   "color_strip.composite.error.min_layers": "至少需要 1 个图层",
   "color_strip.composite.error.no_source": "每个图层必须选择一个源",