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/api/review.go

@@ -63,13 +63,18 @@ func (s *Server) handleResolveReview(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if _, ok, err := s.DB.GetWorkoutKind(r.Context(), body.WorkoutKindID); err != nil {
+	kind, ok, err := s.DB.GetWorkoutKind(r.Context(), body.WorkoutKindID)
+	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
 	} else if !ok {
 		writeError(w, http.StatusBadRequest, "workout kind not found")
 		return
 	}
+	if kind.Name == "Race" {
+		writeError(w, http.StatusBadRequest, "Race is assigned automatically from Garmin metadata and cannot be set manually")
+		return
+	}
 
 	kindID := body.WorkoutKindID
 	if _, err := s.DB.InsertKindAssignment(r.Context(), store.KindAssignment{