fix(backend): harden final MVP invariants

backend/internal/logic/ai/handlers.go

@@ -39,8 +39,8 @@ func NewHandler(service *SessionService) *Handler {
 }
 
 func (h *Handler) Register(router gin.IRouter) {
-	router.GET("/projects/:projectId/ai-sessions", h.list)
-	router.POST("/projects/:projectId/ai-sessions", h.create)
+	router.GET("/projects/:id/ai-sessions", h.list)
+	router.POST("/projects/:id/ai-sessions", h.create)
 }
 
 func (h *Handler) list(c *gin.Context) {
@@ -84,7 +84,7 @@ func aiRequestContext(c *gin.Context) (uint, string, bool) {
 		httpx.Error(c, http.StatusUnauthorized, "unauthorized", "未登录或登录已失效")
 		return 0, "", false
 	}
-	projectIdentity, ok := httpx.IdentityParam(c, "projectId")
+	projectIdentity, ok := httpx.IdentityParam(c, "id")
 	if !ok {
 		return 0, "", false
 	}

backend/internal/logic/ai/rate_limit_postgres_test.go

@@ -1,3 +1,5 @@
+//go:build integration
+
 package ai
 
 import (
@@ -16,10 +18,8 @@ import (
 )
 
 func TestPostgresReserveRateLimitIsAtomicAcrossConcurrentConnections(t *testing.T) {
-	dsn := os.Getenv("DATABASE_URL")
-	if dsn == "" {
-		t.Skip("DATABASE_URL is not configured; skipping PostgreSQL AI rate reservation test")
-	}
+	dsn := os.Getenv("TEST_DATABASE_URL")
+	require.NotEmpty(t, dsn, "TEST_DATABASE_URL is required for integration tests and must point to an isolated database")
 	database, err := gorm.Open(postgres.Open(dsn), &gorm.Config{TranslateError: true, Logger: logger.Default.LogMode(logger.Silent)})
 	require.NoError(t, err)
 	require.NoError(t, models.AutoMigrate(database))