Rework API input CSS: segments, remove led_count, HAOS light, test preview

API Input CSS rework:
- Remove led_count field from ApiInputColorStripSource (always auto-sizes)
- Add segment-based payload: solid, per_pixel, gradient modes
- Segments applied in order (last wins on overlap), auto-grow buffer
- Backward compatible: legacy {"colors": [...]} still works
- Pydantic validation: mode-specific field requirements

Test preview:
- Enable test preview button on api_input cards
- Hide LED/FPS controls for api_input (sender controls those)
- Show input source selector for all CSS tests (preselected)
- FPS sparkline chart using shared createFpsSparkline (same as target cards)
- Server only sends frames when push_generation changes (no idle frames)

HAOS integration:
- New light.py: ApiInputLight entity per api_input source (RGB + brightness)
- turn_on pushes solid segment, turn_off pushes fallback color
- Register wled_screen_controller.set_leds service for arbitrary segments
- New services.yaml with field definitions
- Coordinator: push_colors() and push_segments() methods
- Platform.LIGHT added to platforms list

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

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

@@ -312,6 +312,10 @@
   "device.tip.webui": "打开设备内置的 Web 界面进行高级配置",
   "device.tip.add": "点击此处添加新的 LED 设备",
   "settings.title": "设置",
+  "settings.tab.general": "常规",
+  "settings.tab.backup": "备份",
+  "settings.tab.mqtt": "MQTT",
+  "settings.logs.open_viewer": "打开日志查看器",
   "settings.general.title": "常规设置",
   "settings.capture.title": "采集设置",
   "settings.capture.saved": "采集设置已更新",
@@ -1076,6 +1080,7 @@
   "color_strip.test.error": "无法连接到预览流",
   "color_strip.test.led_count": "LED数量:",
   "color_strip.test.fps": "FPS:",
+  "color_strip.test.receive_fps": "接收帧率",
   "color_strip.test.apply": "应用",
   "color_strip.test.composite": "合成",
   "color_strip.preview.title": "实时预览",