V3-01: activity type per ride

Adds Activity (motorcycle/bicycle/scooter/skateboard/running/walking/other) as
a column on Trip, and threads it through as real behaviour rather than a label:
ActivityProfile (domain/activity_profile.dart) carries a noise floor, accuracy
gate, histogram bucket width, and elevation smoothing window/threshold per
activity, consumed by sanitizeSpeedKmh, isUsableFix, computeSummary, Accumulator
and speedHistogram. The motorcycle profile reproduces the exact constants the
app shipped with before this existed, and a test asserts they never drift apart.

This is the port's first real migration: schemaVersion 1 -> 2,
m.addColumn(trips, trips.activity) with a motorcycle default so every existing
row survives unmodified. Proven with a hand-built v1 SQLite file (raw sqlite3,
not drift_dev's schema tooling) that a real database with real rides upgrades
and keeps every trip, segment and point.

No picker in front of Start: a new trip defaults to whichever activity was most
recently used, derived live from the trips table rather than duplicated into a
Config field. Editable afterwards on trip detail, which recomputes aggregates
under the new profile immediately -- a walking pace that reads as noise under a
motorcycle's floor reads as real movement once the activity is corrected, and
there's a test proving exactly that transition.

The widget-test pass for the activity-picker sheet caught a real overflow bug:
seven options overflowed a Column-based bottom sheet the same way the record
screen once did. Fixed with a scrollable ListView + isScrollControlled, same
shape as that earlier fix.

188 tests (171 -> 188): 2 migration, 5 ActivityProfile, 3 profile-threading
proofs in computeSummary, 5 repository, 2 widget. Analyze clean.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test/widget_test.dart

@@ -7,6 +7,7 @@ import 'package:rippr/src/app/providers.dart';
 import 'package:rippr/src/data/database.dart';
 import 'package:rippr/src/data/trip_repository.dart';
 import 'package:rippr/src/domain/models.dart';
+import 'package:rippr/src/ui/activity_display.dart';
 import 'package:rippr/src/recording/location_source.dart';
 import 'package:rippr/src/ui/detail/trip_detail_screen.dart';
 import 'package:rippr/src/ui/record/record_screen.dart';
@@ -282,6 +283,27 @@ void main() {
 
       expect(await repo.tripById(a), isNull);
     });
+
+    screenTest('a tile shows its own activity icon (V3-01)', (tester) async {
+      final motorcycleTrip =
+          await seedCompletedTrip(startedAt: 1000, endedAt: 5000, name: 'Ride');
+      final bikeTrip =
+          await seedCompletedTrip(startedAt: 10000, endedAt: 15000, name: 'Bike');
+      await repo.setActivity(bikeTrip, Activity.bicycle);
+
+      await tester.pumpWidget(host(const TripsScreen()));
+      await tester.pumpAndSettle();
+
+      Icon iconFor(int tripId) => tester.widget<Icon>(
+            find.descendant(
+              of: find.byKey(Key('trip-$tripId')),
+              matching: find.byType(Icon),
+            ),
+          );
+
+      expect(iconFor(motorcycleTrip).icon, activityIcon(Activity.motorcycle));
+      expect(iconFor(bikeTrip).icon, activityIcon(Activity.bicycle));
+    });
   });
 
   group('trip detail', () {
@@ -340,5 +362,23 @@ void main() {
       expect(find.text('Coast run'), findsOneWidget);
       expect((await repo.tripById(id))!.name, 'Coast run');
     });
+
+    screenTest('editing the activity updates the row and recomputes aggregates',
+        (tester) async {
+      final id = await seedCompletedTrip(startedAt: 1000, endedAt: 5000);
+
+      await tester.pumpWidget(host(TripDetailScreen(tripId: id), map: false));
+      await tester.pumpAndSettle();
+
+      expect(find.text(activityLabel(Activity.motorcycle)), findsOneWidget);
+
+      await tester.tap(find.byKey(const Key('activity-row')));
+      await tester.pumpAndSettle();
+      await tester.tap(find.byKey(Key('activity-${Activity.walking.name}')));
+      await tester.pumpAndSettle();
+
+      expect(find.text(activityLabel(Activity.walking)), findsOneWidget);
+      expect((await repo.tripById(id))!.activity, Activity.walking);
+    });
   });
 }