feat: 实现社区激励金（公户）系统，经济闭环

- 新增 CommunityFund / FundLog 模型（公户余额单行表 + 6种流水类型）
- 新增 FundRepo 仓储（GetBalance / IncrBalance / CreateLog / ListLogs / WithTx）
- 改造 EnergyService 五个方法：Energize 税收入公户、DeductOnRename/DeductOnDeletePost 入公户、RefundOnRenameReject 从公户支出、AdminAdjust 拆分为 admin_transfer/system_operation
- 新增 ErrInsufficientFund 错误哨兵
- 管理后台新增公户余额展示 + 公户流水页面 + 域能调整资金来源选择
- 新增 energy.css / energy.js 前端交互
- 侧边栏新增公户流水入口

internal/repository/fund_repo.go

@@ -0,0 +1,60 @@
+package repository
+
+import (
+	"metazone.cc/metalab/internal/model"
+	"metazone.cc/metalab/internal/service"
+
+	"gorm.io/gorm"
+)
+
+// FundRepo 公户数据访问
+type FundRepo struct {
+	db *gorm.DB
+}
+
+// NewFundRepo 构造函数
+func NewFundRepo(db *gorm.DB) *FundRepo {
+	return &FundRepo{db: db}
+}
+
+// WithTx 基于给定事务连接创建新的 FundRepo
+func (r *FundRepo) WithTx(tx *gorm.DB) service.FundStore {
+	return &FundRepo{db: tx}
+}
+
+// GetBalance 查询公户余额
+func (r *FundRepo) GetBalance() (int, error) {
+	var fund model.CommunityFund
+	err := r.db.First(&fund, 1).Error
+	if err != nil {
+		return 0, err
+	}
+	return fund.Balance, nil
+}
+
+// IncrBalance 原子增减公户余额
+func (r *FundRepo) IncrBalance(amount int) error {
+	return r.db.Model(&model.CommunityFund{}).
+		Where("id = 1").
+		UpdateColumn("balance", gorm.Expr("balance + ?", amount)).Error
+}
+
+// CreateLog 创建公户流水
+func (r *FundRepo) CreateLog(log *model.FundLog) error {
+	return r.db.Create(log).Error
+}
+
+// ListLogs 分页查询公户流水
+func (r *FundRepo) ListLogs(logType string, offset, limit int) ([]model.FundLog, int64, error) {
+	query := r.db.Model(&model.FundLog{})
+	if logType != "" {
+		query = query.Where("type = ?", logType)
+	}
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, err
+	}
+	var logs []model.FundLog
+	err := query.Order("created_at DESC").Offset(offset).Limit(limit).Find(&logs).Error
+	return logs, total, err
+}