🧹 [code health improvement] Remove deprecated getUserModel from UserRepositoryImpl

Removes the deprecated synchronous `getUserModel()` method from `UserRepository.kt` and `UserRepositoryImpl.kt`, and removes the deprecated `userModel` and `getUserModelCopy()` properties from `UserSessionManager.kt`. Updates usages to use the new `getUserModelSuspending()` flow within coroutines. Keeps fragment initialization synchronous in DashboardActivity to prevent a white screen flash.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: dogi

app/src/main/java/org/ole/planet/myplanet/ui/dashboard/DashboardActivity.kt

@@ -137,16 +137,20 @@ class DashboardActivity : DashboardElementActivity(), OnHomeItemClickListener, N
         )
 
         isFirstLaunch = savedInstanceState == null
+        if (isFirstLaunch) handleInitialFragment()
         addBackPressCallback()
         collectUiState()
 
         lifecycleScope.launch {
             user = userSessionManager.getUserModel()
             checkUser()
             updateAppTitle()
-            if (handleGuestAccess()) return@launch
+            if (handleGuestAccess()) {
+                isReady = true
+                binding.root.invalidate()
+                return@launch
+            }
 
-            if (isFirstLaunch) handleInitialFragment()
             initializeDashboard()
             isReady = true
             binding.root.invalidate()