android: add contacts API parity and real contacts screen

android/CHANGELOG.md

@@ -665,3 +665,17 @@
 - Extended message data layer with:
   - `GET /api/v1/messages/{message_id}/thread`
   - `MessageRepository.getMessageThread(...)` for thread/replies usage in upcoming UI steps.
+
+### Step 103 - Contacts API parity + real Contacts screen
+- Added Android integration for contacts endpoints:
+  - `GET /api/v1/users/contacts`
+  - `POST /api/v1/users/{user_id}/contacts`
+  - `POST /api/v1/users/contacts/by-email`
+  - `DELETE /api/v1/users/{user_id}/contacts`
+- Extended `AccountRepository` + `NetworkAccountRepository` with contacts methods.
+- Replaced placeholder Contacts screen with real stateful flow (`ContactsViewModel`):
+  - load contacts from backend,
+  - user search + add contact,
+  - add contact by email,
+  - remove contact,
+  - loading/refresh/error/info states.