feat: update documentation source and add index.md

- Changed documentation source from 'documentation.md' to 'index.md' in content.config.ts.
- Added new index.md file containing comprehensive documentation for ArtMCP, including installation, tools, prompts, resources, MCP integration, and API endpoints.
- Updated GitHub repository configuration in nuxt.config.ts for consistency.
- Bumped dependencies in package.json to latest versions for improved functionality and security.

package.json

@@ -12,13 +12,13 @@
     "lint": "eslint ."
   },
   "dependencies": {
-    "@nuxt/content": "3.8.2",
-    "@nuxt/eslint": "1.11.0",
-    "@nuxthub/core": "0.9.1",
-    "@nuxtjs/mcp-toolkit": "0.4.1",
+    "@nuxt/content": "3.9.0",
+    "@nuxt/eslint": "1.12.1",
+    "@nuxthub/core": "0.10.1",
+    "@nuxtjs/mcp-toolkit": "0.5.2",
     "better-sqlite3": "12.5.0",
     "nuxt": "4.2.1",
-    "nuxt-studio": "1.0.0-alpha.2",
+    "nuxt-studio": "1.0.0-alpha.4",
     "vue": "3.5.25",
     "vue-router": "4.6.3",
     "zod": "4.1.13"