v1.0.18: fix ON_CHANGE never starting, improve version display

- Start FileWatchService from SyncFlowApp.onCreate() for any existing
  enabled ON_CHANGE pairs — previously the watcher only started on
  device boot or explicit pair toggle, so existing pairs after an
  app update never got watched
- About screen now shows "Version X.Y.Z (build N)" updating
  automatically from BuildConfig on every release

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/main/kotlin/com/syncflow/ui/settings/SettingsScreen.kt

@@ -137,11 +137,17 @@ fun SettingsScreen(
             ) {
                 Column(modifier = Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(4.dp)) {
                     Text(
-                        "SyncFlow v${com.syncflow.BuildConfig.VERSION_NAME} — Free, no subscription.",
-                        style = MaterialTheme.typography.bodySmall,
+                        "SyncFlow",
+                        style = MaterialTheme.typography.titleSmall,
                     )
                     Text(
-                        "Open source. No ads. No tracking.",
+                        "Version ${com.syncflow.BuildConfig.VERSION_NAME} (build ${com.syncflow.BuildConfig.VERSION_CODE})",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                    Spacer(Modifier.height(2.dp))
+                    Text(
+                        "Free, no subscription. No ads. No tracking.",
                         style = MaterialTheme.typography.bodySmall,
                         color = MaterialTheme.colorScheme.onSurfaceVariant,
                     )