Add habit HTTP endpoints

- Create DTOs for HTTP requests and responses
- Implement habit handlers (create, get today's, mark)
- Register routes in router: POST /habits, GET /habits/today, POST /habits/{id}/mark
- Add missing repository methods (FindByID, FindByHabitID, FindPendingByHabitID, Delete)
- Wire up dependencies in main.go
- Tested with curl: create, list, mark habits work correctly

internal/infrastructure/http/habit_handlers.go

@@ -0,0 +1,143 @@
+package http
+
+import (
+	"encoding/json"
+	"net/http"
+	"time"
+
+	"habit-tracker-api/internal/application/commands"
+	"habit-tracker-api/internal/application/queries"
+	"habit-tracker-api/internal/shared/errors"
+
+	"github.com/go-chi/chi/v5"
+)
+
+type HabitHandlers struct {
+	createHandler    *commands.CreateHabitHandler
+	getTodaysHandler *queries.GetTodaysHabitsHandler
+	markHandler      *commands.MarkHabitHandler
+}
+
+func NewHabitHandlers(
+	createHandler *commands.CreateHabitHandler,
+	getTodaysHandler *queries.GetTodaysHabitsHandler,
+	markHandler *commands.MarkHabitHandler,
+) *HabitHandlers {
+	return &HabitHandlers{
+		createHandler:    createHandler,
+		getTodaysHandler: getTodaysHandler,
+		markHandler:      markHandler,
+	}
+}
+
+func (h *HabitHandlers) CreateHabit(w http.ResponseWriter, r *http.Request) {
+	var req CreateHabitRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		respondError(w, http.StatusBadRequest, "Invalid request body")
+		return
+	}
+
+	userID := "user-123"
+
+	cmd := commands.CreateHabitCommand{
+		UserID:        userID,
+		Name:          req.Name,
+		Description:   req.Description,
+		Type:          req.Type,
+		Frequency:     req.Frequency,
+		SpecificDays:  req.SpecificDays,
+		SpecificDates: req.SpecificDates,
+		CarryOver:     req.CarryOver,
+		TargetValue:   req.TargetValue,
+	}
+
+	habitID, err := h.createHandler.Handle(r.Context(), cmd)
+	if err != nil {
+		if err == errors.ErrInvalidInput {
+			respondError(w, http.StatusBadRequest, err.Error())
+			return
+		}
+		respondError(w, http.StatusInternalServerError, "Failed to create habit")
+		return
+	}
+
+	respondJSON(w, http.StatusCreated, map[string]string{"id": habitID})
+}
+
+func (h *HabitHandlers) GetTodaysHabits(w http.ResponseWriter, r *http.Request) {
+	userID := "user-123"
+	timezone := "UTC"
+
+	query := queries.GetTodaysHabitsQuery{
+		UserID:   userID,
+		Timezone: timezone,
+		Date:     time.Now().UTC(),
+	}
+
+	habits, err := h.getTodaysHandler.Handle(r.Context(), query)
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "Failed to get habits")
+		return
+	}
+
+	response := make([]TodaysHabitResponse, len(habits))
+	for i, habit := range habits {
+		response[i] = TodaysHabitResponse{
+			ID:            habit.ID,
+			Name:          habit.Name,
+			Type:          habit.Type,
+			TargetValue:   habit.TargetValue,
+			ScheduledDate: habit.ScheduledDate,
+			IsCarriedOver: habit.IsCarriedOver,
+		}
+	}
+
+	respondJSON(w, http.StatusOK, response)
+}
+
+func (h *HabitHandlers) MarkHabit(w http.ResponseWriter, r *http.Request) {
+	habitID := chi.URLParam(r, "id")
+
+	var req MarkHabitRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		respondError(w, http.StatusBadRequest, "Invalid request body")
+		return
+	}
+
+	scheduledDate, err := time.Parse("2006-01-02", req.ScheduledDate)
+	if err != nil {
+		respondError(w, http.StatusBadRequest, "Invalid date format (use YYYY-MM-DD)")
+		return
+	}
+
+	cmd := commands.MarkHabitCommand{
+		HabitID:       habitID,
+		ScheduledDate: scheduledDate,
+		Value:         req.Value,
+	}
+
+	if err := h.markHandler.Handle(r.Context(), cmd); err != nil {
+		if err == errors.ErrAlreadyExists {
+			respondError(w, http.StatusConflict, "Habit already marked for this date")
+			return
+		}
+		if err == errors.ErrNotFound {
+			respondError(w, http.StatusNotFound, "Habit not found")
+			return
+		}
+		respondError(w, http.StatusInternalServerError, "Failed to mark habit")
+		return
+	}
+
+	respondJSON(w, http.StatusOK, map[string]string{"status": "marked"})
+}
+
+func respondJSON(w http.ResponseWriter, status int, data interface{}) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(data)
+}
+
+func respondError(w http.ResponseWriter, status int, message string) {
+	respondJSON(w, status, ErrorResponse{Error: message})
+}