feat: add Skill Hub feature for managing community skills

- Implemented Skill Hub page with tabs for remote, local, and installed skills.
- Added localization support for Chinese in skill-hub.json.
- Created API routes for fetching remote skills, listing local skills, and managing installed skills.
- Developed functionality for installing and uninstalling skills from both remote and local sources.
- Introduced caching mechanism for remote skills and handling updates for installed skills.

ccw/frontend/src/locales/zh/skills.json

@@ -10,7 +10,8 @@
   },
   "location": {
     "project": "项目",
-    "user": "全局"
+    "user": "全局",
+    "hub": "仓库"
   },
   "source": {
     "builtin": "内置",