Add Race workout kind with Garmin eventType auto-detection, sync-time running filter, and pill-based review queue filter

Race is the 8th fixed workout kind, seeded with a real (not placeholder)
rule since Garmin Connect's eventType.typeKey reports "race" for
manually-tagged race activities. Non-running activity types (padel,
cycling, strength training, ...) are now dropped at sync time instead of
being stored. The Review Queue's type filter is now clickable exclusive
pill buttons instead of a dropdown.

backend/internal/sync/service_test.go

@@ -62,6 +62,40 @@ func TestBackfill_StoresActivitiesAndRecordsSyncRun(t *testing.T) {
 	}
 }
 
+func TestBackfill_SkipsNonRunningActivities(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+
+	m := &mock.Client{Activities: []garmin.Activity{
+		{ActivityID: 1, ActivityType: garmin.ActivityType{TypeKey: "running"},
+			StartTimeGMT: "2026-07-01 06:00:00", Distance: 5000, Duration: 1500},
+		{ActivityID: 2, ActivityType: garmin.ActivityType{TypeKey: "trail_running"},
+			StartTimeGMT: "2026-07-02 06:00:00", Distance: 8000, Duration: 2400},
+		{ActivityID: 3, ActivityType: garmin.ActivityType{TypeKey: "paddelball"},
+			StartTimeGMT: "2026-07-03 06:00:00", Distance: 0, Duration: 1800},
+		{ActivityID: 4, ActivityType: garmin.ActivityType{TypeKey: "indoor_cycling"},
+			StartTimeGMT: "2026-07-04 06:00:00", Distance: 0, Duration: 1800},
+	}}
+	svc := NewService(m, db, Config{}, fixedNow(time.Date(2026, 7, 11, 0, 0, 0, 0, time.UTC)))
+
+	if err := svc.Backfill(ctx); err != nil {
+		t.Fatalf("Backfill: %v", err)
+	}
+
+	activities, err := db.ListActivities(ctx, store.ActivityFilter{})
+	if err != nil {
+		t.Fatalf("ListActivities: %v", err)
+	}
+	if len(activities) != 2 {
+		t.Fatalf("expected 2 stored (running-only) activities, got %d: %+v", len(activities), activities)
+	}
+	for _, a := range activities {
+		if a.GarminActivityID != 1 && a.GarminActivityID != 2 {
+			t.Errorf("unexpected non-running activity stored: %+v", a)
+		}
+	}
+}
+
 func TestFillPendingDetailsAndClassify_EndToEnd(t *testing.T) {
 	db := openTestDB(t)
 	ctx := context.Background()
@@ -162,6 +196,21 @@ func TestBuildMetricContext_DerivesExpectedMetrics(t *testing.T) {
 	if got := ctx["lap_interval_pattern"]; got != 0 {
 		t.Errorf("lap_interval_pattern = %v, want 0", got)
 	}
+	if got := ctx["is_race"]; got != 0 {
+		t.Errorf("is_race = %v, want 0 (EventTypeKey not set)", got)
+	}
+}
+
+func TestBuildMetricContext_DerivesIsRace(t *testing.T) {
+	ctx := buildMetricContext(store.Activity{EventTypeKey: "race"}, nil, 0)
+	if got := ctx["is_race"]; got != 1 {
+		t.Errorf("is_race = %v, want 1 when EventTypeKey is \"race\"", got)
+	}
+
+	ctx = buildMetricContext(store.Activity{EventTypeKey: "training"}, nil, 0)
+	if got := ctx["is_race"]; got != 0 {
+		t.Errorf("is_race = %v, want 0 when EventTypeKey is not \"race\"", got)
+	}
 }
 
 func TestBackfill_SecondRunIsANoOpOnceHorizonFullyCovered(t *testing.T) {