feat: dashboard manifest supports 'supported_games' field, frontend filters by selected game

- DashboardTheme model adds supported_games (default: 'all')
- Built-in dashboards declare game compatibility:
  speedometer/tachometer/gear_indicator -> all
  lap_timer -> forza_horizon_5,forza_horizon_4,forza_motorsport,f1_24
- Dashboard browser filters themes by selected game
- Card shows '全' (all) or '限' (limited) badge
- Updated DASHBOARD_DEV.md with supported_games spec

dashboards/gear_indicator/manifest.json

@@ -5,6 +5,7 @@
     "description": "醒目大圆档位显示，适合竖屏手机副屏",
     "author": "Yei.J. (AskaEth)",
     "version": "1.0.0",
+    "supported_games": "all",
     "config": {
         "icon": "⚙️",
         "aspect_ratio": "1:1",

dashboards/lap_timer/manifest.json

@@ -2,9 +2,10 @@
     "id": "lap_timer",
     "name": "圈速计时器",
     "category": "timing",
-    "description": "当前圈速、最佳圈和上圈时间对比显示",
+    "description": "当前圈速、最佳圈和上圈时间对比显示。仅支持 Forza 系列和 F1",
     "author": "Yei.J. (AskaEth)",
     "version": "1.0.0",
+    "supported_games": "forza_horizon_5,forza_horizon_4,forza_motorsport,f1_24",
     "config": {
         "icon": "⏱️",
         "aspect_ratio": "4:3",

dashboards/speedometer/manifest.json

@@ -5,10 +5,10 @@
     "description": "大字号实时速度显示，支持km/h和mph，适合横屏全屏显示",
     "author": "Yei.J. (AskaEth)",
     "version": "1.0.0",
+    "supported_games": "all",
     "config": {
         "icon": "🏎️",
         "unit": "kmh",
-        "show_unit": true,
         "aspect_ratio": "auto",
         "render_mode": "contain"
     }

dashboards/tachometer/manifest.json

@@ -5,6 +5,7 @@
     "description": "赛车风格弧形转速表，支持红区换档提示，推荐横屏",
     "author": "Yei.J. (AskaEth)",
     "version": "1.0.0",
+    "supported_games": "all",
     "config": {
         "icon": "⏱️",
         "max_rpm": 8000,