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/kinds.go

@@ -162,48 +162,3 @@ func (s *Server) handleUpdateWorkoutKind(w http.ResponseWriter, r *http.Request)
 	}
 	writeJSON(w, http.StatusOK, resp)
 }
-
-// handleReclassifyKind re-runs the rule engine for every activity currently
-// assigned to (or under review for) this kind. It's a synchronous, bounded
-// operation (unlike sync), so it runs inline rather than in the background.
-func (s *Server) handleReclassifyKind(w http.ResponseWriter, r *http.Request) {
-	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
-	if err != nil {
-		writeError(w, http.StatusBadRequest, "invalid workout kind id")
-		return
-	}
-
-	assignments, err := s.DB.AssignmentsForKind(r.Context(), id)
-	if err != nil {
-		writeError(w, http.StatusInternalServerError, err.Error())
-		return
-	}
-	reviewQueue, err := s.DB.ReviewQueue(r.Context())
-	if err != nil {
-		writeError(w, http.StatusInternalServerError, err.Error())
-		return
-	}
-
-	seen := make(map[int64]bool)
-	var activityIDs []int64
-	for _, a := range assignments {
-		if !seen[a.ActivityID] {
-			seen[a.ActivityID] = true
-			activityIDs = append(activityIDs, a.ActivityID)
-		}
-	}
-	for _, a := range reviewQueue {
-		if !seen[a.ActivityID] {
-			seen[a.ActivityID] = true
-			activityIDs = append(activityIDs, a.ActivityID)
-		}
-	}
-
-	for _, activityID := range activityIDs {
-		if err := s.Sync.ClassifyActivity(r.Context(), activityID); err != nil {
-			writeError(w, http.StatusInternalServerError, err.Error())
-			return
-		}
-	}
-	writeJSON(w, http.StatusOK, map[string]int{"reclassified": len(activityIDs)})
-}