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/index.ts

@@ -40,6 +40,7 @@ import help from './help.json';
 import cliViewer from './cli-viewer.json';
 import team from './team.json';
 import terminalDashboard from './terminal-dashboard.json';
+import skillHub from './skill-hub.json';
 
 /**
  * Flattens nested JSON object to dot-separated keys
@@ -103,4 +104,5 @@ export default {
   ...flattenMessages(cliViewer, 'cliViewer'),
   ...flattenMessages(team, 'team'),
   ...flattenMessages(terminalDashboard, 'terminalDashboard'),
+  ...flattenMessages(skillHub, 'skillHub'),
 } as Record<string, string>;