V3-12: crash reporting (code only)

shouldInitializeCrashReporting() and scrubExtra() are pure, fully unit-tested decision/scrubbing functions wired into sentry_flutter via beforeSend/beforeBreadcrumb. Config.crashReportingEnabled defaults off; the DSN is a compile-time --dart-define, not a preference. RecordingEngine gained an injected onUnexpectedStop callback, firing once when restoreAfterProcessDeath finds a trip still 'recording' at launch -- the process died without a user stop.

Marked partially done: the ticket's real acceptance criteria (a forced crash landing in a real Sentry project from a release build, inspecting a real payload) need a Sentry account and a release build this environment can't produce.

lib/main.dart

@@ -3,11 +3,22 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import 'src/app/providers.dart';
 import 'src/config/config.dart';
+import 'src/crash/crash_reporter.dart';
 import 'src/ui/router.dart';
 import 'src/ui/theme.dart';
 
-void main() {
-  runApp(const ProviderScope(child: RipprApp()));
+Future<void> main() async {
+  // Loaded early, once, purely to decide whether to talk to Sentry at all -- the
+  // decision has to be made before `runApp`, since `SentryFlutter.init` wraps it. The
+  // widget tree loads its own `Config` again in `RipprApp.initState` for everything
+  // else; SharedPreferences is memory-cached after the first read, so this costs nothing
+  // beyond a single extra map lookup.
+  WidgetsFlutterBinding.ensureInitialized();
+  final config = await Config.load();
+  await maybeInitCrashReporting(
+    config: config,
+    appRunner: () async => runApp(const ProviderScope(child: RipprApp())),
+  );
 }
 
 class RipprApp extends ConsumerStatefulWidget {