feat: add Unsplash search hook and API proxy routes

- Implemented `useUnsplashSearch` hook for searching Unsplash photos with debounce.
- Created Unsplash API client functions for searching photos and triggering downloads.
- Added proxy routes for Unsplash API to handle search requests and background image uploads.
- Introduced accessibility utilities for WCAG compliance checks and motion preference management.
- Developed theme sharing module for encoding and decoding theme configurations as base64url strings.

ccw/frontend/src/locales/en/mcp-manager.json

@@ -132,6 +132,10 @@
       "ask_question": {
         "name": "ask_question",
         "desc": "Ask interactive questions through A2UI interface"
+      },
+      "smart_search": {
+        "name": "smart_search",
+        "desc": "Intelligent code search with fuzzy and semantic modes"
       }
     },
     "paths": {