Improve email verification flow and error handling

- Send verification email before creating user to prevent orphaned accounts
- Detect SMTP authentication errors and fail fast without retries
- Add field-level validation errors for better frontend UX
- Configure docker-compose with explicit environment variables
- Document dollar sign escaping in .env.example (use $$)
- Implement welcome email on successful verification
- Clean up unnecessary comments

internal/infrastructure/http/user_handlers.go

@@ -0,0 +1,51 @@
+package http
+
+import (
+	"net/http"
+
+	"apocapoc-api/internal/application/commands"
+	"apocapoc-api/internal/shared/errors"
+)
+
+type UserHandlers struct {
+	deleteUserHandler *commands.DeleteUserHandler
+}
+
+func NewUserHandlers(deleteUserHandler *commands.DeleteUserHandler) *UserHandlers {
+	return &UserHandlers{
+		deleteUserHandler: deleteUserHandler,
+	}
+}
+
+// DeleteAccount godoc
+// @Summary Delete user account
+// @Description Permanently delete the authenticated user's account and all associated data (habits, entries, tokens). This action cannot be undone.
+// @Tags users
+// @Security BearerAuth
+// @Produce json
+// @Success 200 {object} map[string]string "Account deleted successfully"
+// @Failure 401 {object} ErrorResponse "Unauthorized - invalid or missing token"
+// @Failure 404 {object} ErrorResponse "User not found"
+// @Failure 500 {object} ErrorResponse "Internal server error"
+// @Router /users/me [delete]
+func (h *UserHandlers) DeleteAccount(w http.ResponseWriter, r *http.Request) {
+	userID := r.Context().Value("user_id").(string)
+
+	cmd := commands.DeleteUserCommand{
+		UserID: userID,
+	}
+
+	err := h.deleteUserHandler.Handle(r.Context(), cmd)
+	if err != nil {
+		if err == errors.ErrNotFound {
+			respondError(w, http.StatusNotFound, "User not found")
+			return
+		}
+		respondError(w, http.StatusInternalServerError, "Failed to delete account")
+		return
+	}
+
+	respondJSON(w, http.StatusOK, map[string]string{
+		"message": "Account deleted successfully",
+	})
+}