fix: complete audit security and frontend gaps

backend/internal/auth/middleware.go

@@ -26,3 +26,12 @@ func RequireUser(tokenVerifier func(string) (uint, error)) gin.HandlerFunc {
 		c.Next()
 	}
 }
+
+func CurrentUserID(c *gin.Context) (uint, bool) {
+	value, ok := c.Get(CurrentUserIDKey)
+	if !ok {
+		return 0, false
+	}
+	userID, ok := value.(uint)
+	return userID, ok && userID > 0
+}