Enhance user profile management and Gravatar integration

- Added email field to user profile API and frontend components for better user identification.
- Implemented PATCH /map/api/me endpoint to update user email, enhancing user experience.
- Introduced useGravatarUrl composable for generating Gravatar URLs based on user email.
- Updated profile and layout components to display user avatars using Gravatar, improving visual consistency.
- Enhanced development documentation to guide testing of navbar and profile features.

frontend-nuxt/package.json

@@ -19,6 +19,7 @@
   },
   "dependencies": {
     "leaflet": "^1.9.4",
+    "md5": "^2.3.0",
     "nuxt": "^3.21.1",
     "vue": "^3.5.13",
     "vue-router": "^4.5.0"