feat: confirm dialog before starting sync on mobile data

Replace the disabled-Start + secondary-Start-Anyway button pattern
with a single always-enabled Start button that shows an AlertDialog
when the connection is metered/mobile, requiring explicit confirmation
before running a potentially gigabyte-scale operation.

https://claude.ai/code/session_01U8qF9mK4UBvXsXP1zNMXfX

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/relays/eventsync/EventSyncScreen.kt

@@ -31,6 +31,7 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Card
@@ -40,8 +41,12 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
@@ -63,6 +68,7 @@ fun EventSyncScreen(
 
     val syncState by syncViewModel.syncState.collectAsStateWithLifecycle()
     val isMobileOrMetered by accountViewModel.settings.isMobileOrMeteredConnection.collectAsStateWithLifecycle()
+    var showMobileDataDialog by remember { mutableStateOf(false) }
 
     Scaffold(
         topBar = {
@@ -152,20 +158,17 @@ fun EventSyncScreen(
                 is EventSyncViewModel.SyncState.Error,
                 -> {
                     Button(
-                        onClick = { syncViewModel.start() },
+                        onClick = {
+                            if (isMobileOrMetered) {
+                                showMobileDataDialog = true
+                            } else {
+                                syncViewModel.start()
+                            }
+                        },
                         modifier = Modifier.fillMaxWidth(),
-                        enabled = !isMobileOrMetered || syncState !is EventSyncViewModel.SyncState.Idle,
                     ) {
                         Text(stringRes(R.string.event_sync_start))
                     }
-                    if (isMobileOrMetered && syncState is EventSyncViewModel.SyncState.Idle) {
-                        OutlinedButton(
-                            onClick = { syncViewModel.start() },
-                            modifier = Modifier.fillMaxWidth(),
-                        ) {
-                            Text(stringRes(R.string.event_sync_start_anyway))
-                        }
-                    }
                 }
 
                 is EventSyncViewModel.SyncState.Running -> {
@@ -182,6 +185,29 @@ fun EventSyncScreen(
                 }
             }
 
+            if (showMobileDataDialog) {
+                AlertDialog(
+                    onDismissRequest = { showMobileDataDialog = false },
+                    title = { Text(stringRes(R.string.event_sync_mobile_data_dialog_title)) },
+                    text = { Text(stringRes(R.string.event_sync_wifi_warning)) },
+                    confirmButton = {
+                        Button(
+                            onClick = {
+                                showMobileDataDialog = false
+                                syncViewModel.start()
+                            },
+                        ) {
+                            Text(stringRes(R.string.event_sync_start_anyway))
+                        }
+                    },
+                    dismissButton = {
+                        TextButton(onClick = { showMobileDataDialog = false }) {
+                            Text(stringRes(R.string.event_sync_cancel))
+                        }
+                    },
+                )
+            }
+
             Spacer(Modifier.height(16.dp))
         }
     }

amethyst/src/main/res/values/strings.xml

@@ -1760,6 +1760,7 @@
     <string name="event_sync_step2">Download all events that mention you and send them to your inbox relays.</string>
     <string name="event_sync_step3">Download all direct messages addressed to you and send them to your DM relays.</string>
     <string name="event_sync_wifi_warning">⚠ You appear to be on a metered or mobile connection. This operation can transfer a very large amount of data. Connect to Wi-Fi before starting.</string>
+    <string name="event_sync_mobile_data_dialog_title">Use Mobile Data?</string>
     <string name="event_sync_start">Start Sync</string>
     <string name="event_sync_start_anyway">Start Anyway (mobile data)</string>
     <string name="event_sync_cancel">Cancel</string>