Replace per-kind reclassify with a single global reclassify that respects manual and Race locks

Manual assignments are the user's definitive word and Race assignments come
from a hard Garmin fact (eventType.typeKey), not a retunable rule -- neither
is ever touched by reclassify again, and Race can no longer be set by hand
via the review queue. Adds an Activities page so this locked/unlocked status
is visible per workout, since Review Queue only ever showed unresolved items.

backend/internal/store/workoutkinds.go

@@ -65,6 +65,19 @@ func (db *DB) GetWorkoutKind(ctx context.Context, id int64) (WorkoutKind, bool,
 	return k, true, nil
 }
 
+// GetWorkoutKindByName fetches one workout kind by its unique name.
+func (db *DB) GetWorkoutKindByName(ctx context.Context, name string) (WorkoutKind, bool, error) {
+	row := db.QueryRowContext(ctx, `SELECT `+workoutKindColumns+` FROM workout_kinds WHERE name = ?`, name)
+	k, err := scanWorkoutKind(row)
+	if err == sql.ErrNoRows {
+		return WorkoutKind{}, false, nil
+	}
+	if err != nil {
+		return WorkoutKind{}, false, fmt.Errorf("get workout kind %q: %w", name, err)
+	}
+	return k, true, nil
+}
+
 // ListWorkoutKinds returns workout kinds. If activeOnly, soft-deleted
 // (is_active=0) kinds are excluded.
 func (db *DB) ListWorkoutKinds(ctx context.Context, activeOnly bool) ([]WorkoutKind, error) {