fix: resolve 6 frontend-mobile build and runtime issues

- Add missing User type fields (first_name, last_name, email, avatar_url,
  city, address) used in profile.tsx
- Fix expo-constants import to use namespace import (consistent with
  rest of codebase)
- Replace placeholder production API URL with configurable value
- Fix avatar preset/color selection passing require() IDs to Image uri
  by tracking local source separately
- Replace all relative fetch() calls with configured axios instance
  (relative URLs don't resolve in React Native)

apps/frontend-mobile/constants/config.ts

@@ -1,11 +1,11 @@
-import Constants from 'expo-constants';
+import * as Constants from 'expo-constants';
 
 const ENV = {
   development: {
     API_BASE_URL: 'http://localhost:3001/api',
   },
   production: {
-    API_BASE_URL: 'https://your-production-api.com/api',
+    API_BASE_URL: Constants.expoConfig?.extra?.apiUrl || 'https://api.farmafinder.com/api',
   },
 };