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/src/config/config.dart

@@ -16,6 +16,7 @@ const _keyDeviceId = 'device_id';
 const _keyMapEnabled = 'map_enabled';
 const _keyUnitSystem = 'unit_system';
 const _keyMountedMode = 'mounted_mode';
+const _keyCrashReportingEnabled = 'crash_reporting_enabled';
 
 /// Countries that did not adopt metric for everyday distances. Not exhaustive — a
 /// best-effort default, not a claim of authority. Anyone can override it in Settings.
@@ -78,6 +79,15 @@ class Config {
   Future<void> setMountedMode(bool enabled) =>
       _prefs.setBool(_keyMountedMode, enabled);
 
+  /// V3-12: off until a privacy policy exists (see `docs/LAUNCH.md`) -- crash reporting
+  /// in a location app is a privacy surface, and shipping it on by default ahead of a
+  /// published policy would be the wrong order of operations.
+  bool get crashReportingEnabled =>
+      _prefs.getBool(_keyCrashReportingEnabled) ?? false;
+
+  Future<void> setCrashReportingEnabled(bool enabled) =>
+      _prefs.setBool(_keyCrashReportingEnabled, enabled);
+
   /// Stable per-install id so a server can distinguish riders in a group.
   String get deviceId {
     final existing = _prefs.getString(_keyDeviceId);