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/navigation.json

@@ -36,7 +36,8 @@
     "explorer": "文件浏览器",
     "graph": "图浏览器",
     "teams": "团队执行",
-    "terminalDashboard": "终端仪表板"
+    "terminalDashboard": "终端仪表板",
+    "skillHub": "技能中心"
   },
   "sidebar": {
     "collapse": "收起",