Dedup Garmin data storage, configurable chart colors, taxonomy fixes, sync/progression fixes

- Remove duplicated Garmin fields from storage; decode display-only fields
  (activity name/type, lap duration/HR, structured workout raw JSON) from
  RawJSON at API-response time instead of storing redundant columns
- Add a fully configurable chart color system (pace/HR main-line colors, 4
  effort-kind colors, tint/darken/brighten intensity knobs) under Profile >
  Chart colors
- Rename training types and fix their display order (Easy, Long, 60'/30'
  Threshold, Tempo, Intervals, MAS Test, Race) everywhere they're listed
- Add an Efficiency Factor progression metric; fix Progression chart axes to
  use tight non-zero-based domains, m:ss/km pace formatting, and rounded
  ticks instead of raw floating-point labels
- Expose the raw get_workout_by_id() payload in the raw-data viewer
  alongside activity/lap/detail JSON; enlarge the modal and shrink array
  indentation for readability
- Fix "last sync" reporting a meaningless activity count: record one
  combined sync run per manual "Sync now" and count genuinely new
  activities instead of re-listing whatever Garmin returned for the queried
  window
- Let a Review Queue activity be manually cleared back to Unclassified, and
  make "Reset all" available even while disconnected from Garmin

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

backend/internal/api/activities.go

@@ -13,7 +13,7 @@ import (
 // current classification so the frontend can show what kind it's assigned
 // to and whether that assignment is locked (see Locked's doc comment).
 type activityListItem struct {
-	store.Activity
+	activityResponse
 	WorkoutKindID    *int64  `json:"workout_kind_id"`
 	WorkoutKindName  *string `json:"workout_kind_name"`
 	AssignmentSource *string `json:"assignment_source"`
@@ -55,7 +55,7 @@ func (s *Server) handleListActivities(w http.ResponseWriter, r *http.Request) {
 
 	resp := make([]activityListItem, 0, len(activities))
 	for _, a := range activities {
-		item := activityListItem{Activity: a}
+		item := activityListItem{activityResponse: toActivityResponse(a)}
 		assignment, ok, err := s.DB.CurrentAssignment(r.Context(), a.ID)
 		if err != nil {
 			writeError(w, http.StatusInternalServerError, err.Error())
@@ -107,7 +107,7 @@ func (s *Server) handleGetActivity(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	resp := map[string]any{"activity": activity, "laps": laps}
+	resp := map[string]any{"activity": toActivityResponse(activity), "laps": toLapResponses(laps)}
 	if hasAssignment {
 		resp["assignment"] = assignment
 	}