Initial commit: Material Texture API service

- Go + Gin + GORM + PostgreSQL backend
- RESTful API for material management
- Docker deployment support
- Database partitioning for billion-scale data
- API documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/models/binding.go

@@ -0,0 +1,54 @@
+package models
+
+import (
+	"time"
+)
+
+type MaterialBinding struct {
+	ID         int64     `json:"id" gorm:"primaryKey;autoIncrement"`
+	MaterialID int64     `json:"material_id" gorm:"not null;index:idx_bindings_material_id"`
+	GroupID    string    `json:"group_id" gorm:"size:255;not null;index:idx_bindings_group_id"`
+	CreatedAt  time.Time `json:"created_at" gorm:"autoCreateTime"`
+
+	// 关联的材质（用于预加载）
+	Material *Material `json:"material,omitempty" gorm:"foreignKey:MaterialID;constraint:OnDelete:CASCADE"`
+}
+
+func (MaterialBinding) TableName() string {
+	return "material_bindings"
+}
+
+// 绑定请求 - 一个材质绑定到多个group_id
+type BindingRequest struct {
+	GroupIDs []string `json:"group_ids" binding:"required,min=1,max=10000"`
+}
+
+// 解绑请求
+type UnbindRequest struct {
+	GroupIDs []string `json:"group_ids" binding:"required,min=1,max=10000"`
+}
+
+// 批量查询group_id关联材质的请求
+type GroupMaterialsRequest struct {
+	GroupIDs []string `json:"group_ids" binding:"required,min=1,max=10000"`
+}
+
+// 批量查询结果 - 包含材质详情
+type GroupMaterialResult struct {
+	GroupID  string    `json:"group_id"`
+	Material *Material `json:"material"`
+}
+
+// GetGroups 分页查询参数
+type GroupListQuery struct {
+	Page     int `form:"page"`
+	PageSize int `form:"page_size"`
+}
+
+// GetGroups 分页响应
+type GroupListResponse struct {
+	Items    []string `json:"items"`
+	Total    int64    `json:"total"`
+	Page     int      `json:"page"`
+	PageSize int      `json:"page_size"`
+}