refactor(core): decouple gin from pkg/util and reduce code duplication

backend/pkg/ginutil/context.go

@@ -0,0 +1,23 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package ginutil provides helper utilities for Gin web framework contexts.
+package ginutil
+
+import "github.com/gin-gonic/gin"
+
+// GetFromContext retrieves a typed value from Gin context.
+func GetFromContext[T any](c *gin.Context, key string) (T, bool) {
+	value, exists := c.Get(key)
+	if !exists {
+		var zero T
+		return zero, false
+	}
+	typed, ok := value.(T)
+	return typed, ok
+}
+
+// SetToContext sets a typed value into Gin context.
+func SetToContext[T any](c *gin.Context, key string, value T) {
+	c.Set(key, value)
+}