feat: allow editing frequency and target_value on habits

- Add frequency to UpdateHabitRequest (was immutable, now editable)
- Validate frequency + specific_days/dates coherence on update
- Keep type and is_negative immutable (they change entry semantics)
- Remove completion_rate references from swagger and README

internal/infrastructure/http/dto.go

@@ -20,12 +20,13 @@ type CreateHabitRequest struct {
 }
 
 type UpdateHabitRequest struct {
-	Name          string   `json:"name"`
-	Description   string   `json:"description"`
-	SpecificDays  []int    `json:"specific_days,omitempty"`
-	SpecificDates []int    `json:"specific_dates,omitempty"`
-	CarryOver     bool     `json:"carry_over"`
-	TargetValue   *float64 `json:"target_value,omitempty"`
+	Name          string                  `json:"name"`
+	Description   string                  `json:"description"`
+	Frequency     value_objects.Frequency `json:"frequency"`
+	SpecificDays  []int                   `json:"specific_days,omitempty"`
+	SpecificDates []int                   `json:"specific_dates,omitempty"`
+	CarryOver     bool                    `json:"carry_over"`
+	TargetValue   *float64                `json:"target_value,omitempty"`
 }
 
 type HabitResponse struct {

internal/infrastructure/http/habit_handlers.go

@@ -313,10 +313,11 @@ func (h *HabitHandlers) UpdateHabit(w http.ResponseWriter, r *http.Request) {
 		UserID:        userID,
 		Name:          req.Name,
 		Description:   req.Description,
-		CarryOver:     req.CarryOver,
-		TargetValue:   req.TargetValue,
+		Frequency:     req.Frequency,
 		SpecificDays:  req.SpecificDays,
 		SpecificDates: req.SpecificDates,
+		CarryOver:     req.CarryOver,
+		TargetValue:   req.TargetValue,
 	}
 
 	if err := h.updateHandler.Handle(r.Context(), cmd); err != nil {

internal/infrastructure/http/habit_integration_test.go

@@ -89,6 +89,7 @@ func TestHabitCRUDFlow(t *testing.T) {
 		reqBody := UpdateHabitRequest{
 			Name:        "Morning Exercise",
 			Description: "Updated description",
+			Frequency:   "DAILY",
 		}
 
 		rr := makeRequest(t, *ts.Router, "PUT", "/api/v1/habits/"+habitID, reqBody, token)

internal/infrastructure/http/stats_handlers.go

@@ -27,7 +27,7 @@ func NewStatsHandlers(
 
 // GetHabitStats godoc
 // @Summary Get habit statistics
-// @Description Get statistics for a specific habit including streaks and completion rates
+// @Description Get statistics for a specific habit including streaks and completions
 // @Tags stats
 // @Produce json
 // @Security BearerAuth

internal/infrastructure/http/stats_integration_test.go

@@ -120,7 +120,8 @@ func TestHabitUpdateAffectsStats(t *testing.T) {
 
 	t.Run("Stats remain after updating habit name", func(t *testing.T) {
 		updateReq := UpdateHabitRequest{
-			Name: "Morning Running",
+			Name:      "Morning Running",
+			Frequency: "DAILY",
 		}
 		rr := makeRequest(t, *ts.Router, "PUT", "/api/v1/habits/"+habitID, updateReq, token)
 		if rr.Code != http.StatusOK {