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/types/api.ts

@@ -1,6 +1,7 @@
 export interface MeResponse {
   username: string
   auths: string[]
+  email?: string
   tokens?: string[]
   prefix?: string
 }