chore(frontend): engineering baseline per guide ch.8

- toolchain: vitest+jsdom (15 tests green: permission pure functions
  exhaustive, storage migration), prettier (printWidth 120 to fit the
  dense existing style + 700-line page budget), commitlint conventional
- npm scripts: typecheck / format / test / lint:fix; build fingerprint
  __APP_VERSION__ (version+git hash+build time) shown in Settings > about
- git hooks via core.hooksPath=frontend/.husky: pre-commit lint-staged
  (prettier + eslint --fix best-effort), commit-msg commitlint
- permission pure functions extracted to lib/permissions.ts (single
  source consumed by useAuth/useLogin); AuditLogsPage filters on URL
- backend: resp package unit tests; health version constant aligned
  with frontend package.json

backend/internal/handler/resp/resp_test.go

@@ -0,0 +1,85 @@
+package resp
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func setupRouter() *gin.Engine {
+	gin.SetMode(gin.TestMode)
+	r := gin.New()
+	return r
+}
+
+func decode(t *testing.T, w *httptest.ResponseRecorder) map[string]any {
+	t.Helper()
+	var m map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &m); err != nil {
+		t.Fatalf("response not json: %v (%s)", err, w.Body.String())
+	}
+	return m
+}
+
+func TestFailEnvelope(t *testing.T) {
+	r := setupRouter()
+	r.GET("/x", func(c *gin.Context) { BadRequest(c, "参数不合法") })
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x", nil)
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want 400", w.Code)
+	}
+	m := decode(t, w)
+	if m["detail"] != "参数不合法" {
+		t.Fatalf("detail = %v", m["detail"])
+	}
+}
+
+func TestInternalErrSanitizes(t *testing.T) {
+	r := setupRouter()
+	dbErr := errors.New("SQL logic error: no such table: users (database is locked)")
+	r.GET("/x", func(c *gin.Context) { InternalErr(c, dbErr) })
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x", nil)
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("status = %d, want 500", w.Code)
+	}
+	m := decode(t, w)
+	// 客户端不得看到 DB 错误原文
+	if m["detail"] == dbErr.Error() {
+		t.Fatalf("internal error leaked to client: %v", m["detail"])
+	}
+	if m["code"] != "internal" {
+		t.Fatalf("code = %v, want internal", m["code"])
+	}
+}
+
+func TestPageEnvelope(t *testing.T) {
+	r := setupRouter()
+	r.GET("/x", func(c *gin.Context) {
+		Page(c, []string{"a", "b"}, 42, 2, 10)
+	})
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x", nil)
+	r.ServeHTTP(w, req)
+
+	m := decode(t, w)
+	if m["total"].(float64) != 42 || m["page"].(float64) != 2 || m["page_size"].(float64) != 10 {
+		t.Fatalf("pagination envelope wrong: %v", m)
+	}
+	items, ok := m["items"].([]any)
+	if !ok || len(items) != 2 {
+		t.Fatalf("items wrong: %v", m["items"])
+	}
+}