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>

migrations/004_add_version_column.sql

@@ -0,0 +1,11 @@
+-- ============================================
+-- Migration: 004_add_version_column.sql
+-- Purpose: 添加乐观锁版本字段
+-- ============================================
+
+-- 添加 version 字段到 materials 表 (用于乐观锁)
+ALTER TABLE materials
+ADD COLUMN IF NOT EXISTS version BIGINT NOT NULL DEFAULT 0;
+
+-- 注释
+COMMENT ON COLUMN materials.version IS '乐观锁版本号，用于防止并发更新覆盖';