feat(skills): add search functionality to Skills page

- Add search input with Search icon in SkillsPage component
- Implement useMemo-based filtering by skill name, description, and directory
- Display search results count when filtering is active
- Show "no results" message when no skills match the search query
- Add i18n translations for search UI (zh/en)
- Maintain responsive layout and consistent styling with existing UI

src/i18n/locales/en.json

@@ -735,7 +735,10 @@
       "removeSuccess": "Repository {{owner}}/{{name}} removed",
       "removeFailed": "Failed to remove",
       "skillCount": "{{count}} skills detected"
-    }
+    },
+    "search": "Search Skills",
+    "searchPlaceholder": "Search skill name or description...",
+    "noResults": "No matching skills found"
   },
   "deeplink": {
     "confirmImport": "Confirm Import Provider",

src/i18n/locales/zh.json

@@ -735,7 +735,10 @@
       "removeSuccess": "仓库 {{owner}}/{{name}} 已删除",
       "removeFailed": "删除失败",
       "skillCount": "识别到 {{count}} 个技能"
-    }
+    },
+    "search": "搜索技能",
+    "searchPlaceholder": "搜索技能名称或描述...",
+    "noResults": "未找到匹配的技能"
   },
   "deeplink": {
     "confirmImport": "确认导入供应商配置",