feat: Enhance PreferencesManager and SyncRepository for better server settings management and error handling

CollabTableAndroid/app/src/main/java/com/collabtable/app/data/preferences/PreferencesManager.kt

@@ -18,9 +18,14 @@ class PreferencesManager(context: Context) {
     }
 
     fun setServerUrl(url: String) {
-        val cleanUrl = url.trim().let {
-            if (it.endsWith("/")) it else "$it/"
+        val raw = url.trim()
+        if (raw.isBlank()) {
+            // Remove the key entirely to fall back to default URL on reads
+            prefs.edit().remove(KEY_SERVER_URL).apply()
+            _serverUrl.value = getServerUrl()
+            return
         }
+        val cleanUrl = raw.let { if (it.endsWith("/")) it else "$it/" }
         prefs.edit().putString(KEY_SERVER_URL, cleanUrl).apply()
         _serverUrl.value = cleanUrl
     }
@@ -38,13 +43,32 @@ class PreferencesManager(context: Context) {
     }
 
     fun setServerPassword(password: String) {
-        prefs.edit().putString(KEY_SERVER_PASSWORD, password).apply()
+        if (password.isBlank()) {
+            prefs.edit().remove(KEY_SERVER_PASSWORD).apply()
+        } else {
+            prefs.edit().putString(KEY_SERVER_PASSWORD, password).apply()
+        }
+    }
+
+    // Clear sync-related state so the next sync starts from scratch
+    fun clearSyncState() {
+        prefs.edit().remove(KEY_LAST_SYNC_TIMESTAMP).apply()
+    }
+
+    fun clearServerSettings() {
+        prefs.edit()
+            .remove(KEY_SERVER_URL)
+            .remove(KEY_SERVER_PASSWORD)
+            .remove(KEY_LAST_SYNC_TIMESTAMP)
+            .apply()
+        _serverUrl.value = getServerUrl()
     }
 
     companion object {
         private const val KEY_SERVER_URL = "server_url"
         private const val KEY_FIRST_RUN = "first_run"
         private const val KEY_SERVER_PASSWORD = "server_password"
+    private const val KEY_LAST_SYNC_TIMESTAMP = "last_sync_timestamp"
         private const val DEFAULT_SERVER_URL = "http://10.0.2.2:3000/api/"
         
         @Volatile

CollabTableAndroid/app/src/main/java/com/collabtable/app/data/repository/SyncRepository.kt

@@ -121,6 +121,12 @@ class SyncRepository(context: Context) {
 
                 return@withContext Result.success(Unit)
             } else {
+                if (response.code() == 401) {
+                    // Unauthorized: likely bad/missing password. Reset sync baseline and surface a clear error.
+                    Logger.e("Sync", "[ERROR] Unauthorized (401). Check server password in Settings.")
+                    setLastSyncTimestamp(0)
+                    return@withContext Result.failure(Exception("Unauthorized (401). Please verify server password."))
+                }
                 Logger.e("Sync", "[ERROR] Sync failed: HTTP ${response.code()}")
                 return@withContext Result.failure(Exception("Sync failed: ${response.code()}"))
             }

CollabTableAndroid/app/src/main/java/com/collabtable/app/ui/screens/ServerSetupViewModel.kt

@@ -160,6 +160,8 @@ class ServerSetupViewModel(
                         // Password is valid, save both URL and password
                         preferencesManager.setServerUrl(finalUrl)
                         preferencesManager.setServerPassword(password)
+                        // Reset sync baseline for a fresh initial sync on new server
+                        preferencesManager.clearSyncState()
                         preferencesManager.setIsFirstRun(false)
                         ApiClient.setBaseUrl(finalUrl)
                         _validationResult.value = true

CollabTableAndroid/app/src/main/java/com/collabtable/app/ui/screens/SettingsScreen.kt

@@ -11,6 +11,7 @@ import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import com.collabtable.app.R
 import com.collabtable.app.data.database.CollabTableDatabase
+import com.collabtable.app.data.api.ApiClient
 import com.collabtable.app.data.preferences.PreferencesManager
 import com.collabtable.app.data.repository.SyncRepository
 import com.collabtable.app.utils.Logger
@@ -174,10 +175,13 @@ fun SettingsScreen(
                                         CollabTableDatabase.clearDatabase(context)
                                     }
                                     
-                                    // Clear preferences
-                                    preferencesManager.setServerUrl("")
-                                    preferencesManager.setServerPassword("")
+                                    // Clear preferences (URL, password, last sync)
+                                    preferencesManager.clearServerSettings()
                                     preferencesManager.setIsFirstRun(true)
+                                    // Clear in-memory logs as part of local data
+                                    Logger.clear()
+                                    // Reset API client base URL to current preference (default)
+                                    ApiClient.setBaseUrl(preferencesManager.getServerUrl())
                                     
                                     Logger.i("Settings", "Left server successfully")