feat: redesign Dashboard layout with search and recently used tools

- Add search input at top to filter tools by name/description
- Add 'recently used' section showing last 3 used tools as compact chips
- Add 'all tools' section header for the tool card grid
- Track tool usage via new 'app/recentlyUsedTools' storage key
- Update navigateTo to record recently used tools (max 3, LRU order)
- Add i18n keys: dashboard_searchPlaceholder, dashboard_recentlyUsed, dashboard_allTools

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

public/_locales/zh/messages.json

@@ -75,6 +75,18 @@
     "message": "仪表盘",
     "description": "Translation key: dashboard_title"
   },
+  "dashboard_searchPlaceholder": {
+    "message": "搜索工具...",
+    "description": "Translation key: dashboard_searchPlaceholder"
+  },
+  "dashboard_recentlyUsed": {
+    "message": "最近使用",
+    "description": "Translation key: dashboard_recentlyUsed"
+  },
+  "dashboard_allTools": {
+    "message": "全部工具",
+    "description": "Translation key: dashboard_allTools"
+  },
   "timestamp_title": {
     "message": "时间戳",
     "description": "Translation key: timestamp_title"