Simplify scenes to capture only target state, add target selector

- Remove DeviceBrightnessSnapshot and AutomationSnapshot from scene data model
- Simplify capture_current_snapshot and apply_scene_state to targets only
- Remove device/automation dependencies from scene preset API routes
- Add target selector (combobox + add/remove) to scene capture modal
- Fix stale profiles reference bug in scene_preset_store recapture
- Update automation engine call sites for simplified scene functions
- Sync scene presets cache between automations and scene-presets modules

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

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

@@ -630,13 +630,13 @@
   "scenes.description.hint": "此场景功能的可选描述",
   "scenes.color": "卡片颜色：",
   "scenes.color.hint": "仪表盘上场景卡片的强调色",
+  "scenes.targets": "目标:",
+  "scenes.targets.hint": "选择要包含在此场景快照中的目标",
   "scenes.capture": "捕获",
   "scenes.activate": "激活场景",
   "scenes.recapture": "重新捕获当前状态",
   "scenes.delete": "删除场景",
   "scenes.targets_count": "目标",
-  "scenes.devices_count": "设备",
-  "scenes.automations_count": "自动化",
   "scenes.captured": "场景已捕获",
   "scenes.updated": "场景已更新",
   "scenes.activated": "场景已激活",