feat: 添加数据模型和存储层

- model: JobTemplate、SubmitJobRequest、JobHistoryQuery 等模型定义

- store: NewGormDB MySQL 连接池，使用 zap 日志替代 GORM 默认日志

- store: TemplateStore CRUD 操作，支持 GORM AutoMigrate

- NewGormDB 接受 gormLevel 参数，由上层传入配置值

- 完整 TDD 测试覆盖

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/store/mysql_test.go

@@ -0,0 +1,14 @@
+package store
+
+import (
+	"testing"
+
+	"go.uber.org/zap"
+)
+
+func TestNewGormDBInvalidDSN(t *testing.T) {
+	_, err := NewGormDB("invalid:dsn@tcp(localhost:99999)/nonexistent?parseTime=true", zap.NewNop(), "warn")
+	if err == nil {
+		t.Fatal("expected error for invalid DSN, got nil")
+	}
+}