docs: architecture link to user service

ARCHITECTURE.md

@@ -228,7 +228,7 @@ Direct integrations:
 * synchronous to `Mail Service` for auth-code delivery;
 * asynchronous session lifecycle projection into Redis for gateway consumption.
 
-## 3. User Service
+## 3. [User Service](user/README.md)
 
 `User Service` owns user identity and profile as platform-level business data.
 
@@ -918,7 +918,7 @@ Recommended order for implementation is:
 2. **Auth / Session Service** (implemented)  
    Public auth flow, `device_session`, revoke/block lifecycle, gateway session projection.
 
-3. **User Service**  
+3. **User Service** (planned)  
    Platform user identity, roles, tariffs/entitlements, user limits, settings, sanctions, and current `declared_country`.
 
 4. **Mail Service**