Add IconSelect for filter types, audio modes, engine descriptions; fix scroll flash

- Filter type picker: IconSelect with 3-column grid, auto-add on select, removed redundant + button
- Audio mode picker: IconSelect with SVG visualizations for RMS/Peak/Beat
- Capture engine grid: added per-engine icons and localized descriptions
- Fixed scroll flash during icon grid open animation (settled class after transitionend)

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

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

@@ -63,6 +63,12 @@
   "templates.engine.select": "选择引擎...",
   "templates.engine.unavailable": "不可用",
   "templates.engine.unavailable.hint": "此引擎在您的系统上不可用",
+  "templates.engine.mss.desc": "跨平台，纯Python",
+  "templates.engine.dxcam.desc": "DirectX，低延迟",
+  "templates.engine.bettercam.desc": "DirectX，高性能",
+  "templates.engine.camera.desc": "USB/IP摄像头捕获",
+  "templates.engine.scrcpy.desc": "Android屏幕镜像",
+  "templates.engine.wgc.desc": "Windows图形捕获",
   "templates.config": "配置",
   "templates.config.show": "显示配置",
   "templates.config.none": "无额外配置",
@@ -1063,6 +1069,9 @@
   "value_source.mode.rms": "RMS（音量）",
   "value_source.mode.peak": "峰值",
   "value_source.mode.beat": "节拍",
+  "value_source.mode.rms.desc": "平均音量水平",
+  "value_source.mode.peak.desc": "最响时刻追踪",
+  "value_source.mode.beat.desc": "节奏脉冲检测",
   "value_source.auto_gain": "自动增益：",
   "value_source.auto_gain.hint": "自动归一化音频电平，使输出使用完整范围，无论输入音量大小",
   "value_source.auto_gain.enable": "启用自动增益",