feat(#17): CRUD de categorias — API Go + tela Vue + testes unitários

API REST /api/categories (GET/POST/PUT/DELETE) com regras de negócio:
categorias padrão não podem ser excluídas; categorias com transações vinculadas
também bloqueadas. Tela Vue com formulário inline de criação/edição, indicador
visual de categorias padrão e botão de exclusão condicional.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

apps/api/internal/handler/category.go

@@ -0,0 +1,92 @@
+package handler
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strconv"
+
+	"github.com/go-chi/chi/v5"
+
+	"financeiro-carvalho/internal/model"
+	"financeiro-carvalho/internal/repository"
+	"financeiro-carvalho/internal/service"
+)
+
+type CategoryHandler struct {
+	svc *service.CategoryService
+}
+
+func NewCategoryHandler(svc *service.CategoryService) *CategoryHandler {
+	return &CategoryHandler{svc: svc}
+}
+
+func (h *CategoryHandler) List(w http.ResponseWriter, r *http.Request) {
+	cats, err := h.svc.List(r.Context())
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "failed to list categories")
+		return
+	}
+	if cats == nil {
+		cats = []model.Category{}
+	}
+	respondJSON(w, http.StatusOK, cats)
+}
+
+func (h *CategoryHandler) Create(w http.ResponseWriter, r *http.Request) {
+	var in model.CategoryInput
+	if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
+		respondError(w, http.StatusBadRequest, "invalid JSON")
+		return
+	}
+	cat, err := h.svc.Create(r.Context(), in)
+	if err != nil {
+		respondError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	respondJSON(w, http.StatusCreated, cat)
+}
+
+func (h *CategoryHandler) Update(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.Atoi(chi.URLParam(r, "id"))
+	if err != nil {
+		respondError(w, http.StatusBadRequest, "invalid id")
+		return
+	}
+	var in model.CategoryInput
+	if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
+		respondError(w, http.StatusBadRequest, "invalid JSON")
+		return
+	}
+	cat, err := h.svc.Update(r.Context(), id, in)
+	if errors.Is(err, repository.ErrNotFound) {
+		respondError(w, http.StatusNotFound, "category not found")
+		return
+	}
+	if err != nil {
+		respondError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	respondJSON(w, http.StatusOK, cat)
+}
+
+func (h *CategoryHandler) Delete(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.Atoi(chi.URLParam(r, "id"))
+	if err != nil {
+		respondError(w, http.StatusBadRequest, "invalid id")
+		return
+	}
+	err = h.svc.Delete(r.Context(), id)
+	switch {
+	case errors.Is(err, repository.ErrNotFound):
+		respondError(w, http.StatusNotFound, "category not found")
+	case errors.Is(err, service.ErrDefaultCategory):
+		respondError(w, http.StatusConflict, err.Error())
+	case errors.Is(err, service.ErrHasTransactions):
+		respondError(w, http.StatusConflict, err.Error())
+	case err != nil:
+		respondError(w, http.StatusInternalServerError, "failed to delete")
+	default:
+		w.WriteHeader(http.StatusNoContent)
+	}
+}

apps/api/internal/handler/respond.go

@@ -0,0 +1,16 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+func respondJSON(w http.ResponseWriter, status int, data any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(data)
+}
+
+func respondError(w http.ResponseWriter, status int, msg string) {
+	respondJSON(w, status, map[string]string{"error": msg})
+}