feat(dashboard): add npm version update notification

- Add /api/version-check endpoint to check npm registry for updates
- Create version-check.js component with update banner UI
- Add CSS styles for version update banner
- Fix hook manager button event handling (use e.currentTarget)
- Bump version to 6.1.2

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "claude-code-workflow",
-  "version": "6.1.1",
+  "version": "6.1.2",
   "description": "JSON-driven multi-agent development framework with intelligent CLI orchestration (Gemini/Qwen/Codex), context-first architecture, and automated workflow execution",
   "type": "module",
   "main": "ccw/src/index.js",