feat(log): 解耦用户访问日志存储，支持切换日志主库

用户访问日志可在 ClickHouse、PostgreSQL、SQLite 之间切换。
关闭 ClickHouse 时由主库承接写入与查询；切换任务会冻结写入、复制数据后翻转主库。
启动时校验日志主库与运行配置一致，定期清理按各库保留天数删除过期记录。

internal/repository/logstore/logstore.go

@@ -0,0 +1,43 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package logstore abstracts user access-log storage across ClickHouse, PostgreSQL and SQLite.
+package logstore
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	analyticsmodel "github.com/Rain-kl/Wavelet/internal/model/analytics"
+	analyticsrepo "github.com/Rain-kl/Wavelet/internal/repository/analytics"
+)
+
+// ErrMigrating 表示日志数据库正在迁移，当前禁止写入。
+var ErrMigrating = errors.New("log database is migrating, writes are disabled")
+
+// UserAccessLogStore 用户访问日志（w_user_access_logs）。
+type UserAccessLogStore interface {
+	BatchInsert(ctx context.Context, logs []analyticsmodel.UserAccessLog) error
+	DeleteAll(ctx context.Context) (int64, error)
+	DeleteBefore(ctx context.Context, cutoff time.Time) (int64, error)
+	Count(ctx context.Context, filter analyticsrepo.AccessLogFilter) (uint64, error)
+	List(ctx context.Context, filter analyticsrepo.AccessLogFilter, page, pageSize int) ([]analyticsmodel.UserAccessLog, uint64, error)
+	GetDailyTrend(ctx context.Context, days int) ([]analyticsrepo.DailyTrend, error)
+	GetBrowserDistribution(ctx context.Context, startTime time.Time) ([]analyticsrepo.BrowserShare, error)
+	GetTopActiveUsers(ctx context.Context, startTime time.Time, limit int) ([]analyticsrepo.TopUser, error)
+	ListForMigration(ctx context.Context, afterID uint64, limit int) ([]analyticsmodel.UserAccessLog, error)
+	MigrationRange(ctx context.Context) (from, to time.Time, err error)
+	EnsurePartitions(ctx context.Context, from, to time.Time) error
+}
+
+// StatusStore 日志库状态。
+type StatusStore interface {
+	ActiveDatabase(ctx context.Context) (string, error)
+}
+
+// Store 当前生效日志库。
+type Store struct {
+	UserAccessLogs UserAccessLogStore
+	Status         StatusStore
+}