feat(log): decouple log storage from ClickHouse with switchable logstore

- New internal/repository/logstore abstraction: exported domain interfaces
  (AccessLogStore/ObservabilityStore/UserAccessLogStore/StatusStore),
  config-driven provider (Active/Build/Migrating/SetConfigReader), GORM
  implementation for PostgreSQL/SQLite (incl. hourly rollups computed in
  real time, migration listers, PG partition maintenance), and a ClickHouse
  wrapper preserving the native batch path; repository facade delegates to
  logstore; import-lint test enforces apps never import analyticsrepo.
- ClickHouse is now optional: the log DB is either the main DB (postgres
  when database.enabled, else sqlite) or clickhouse; boot validation +
  first-run seed; log_database / log_db_migration are protected keys.
- New user task 切换日志数据库 (of_log_db_switch): freeze log writes,
  drain batch writers, copy all 6 raw log tables by id (preserving IDs)
  with target-partition pre-creation for PG, flip log_database on success,
  clear the freeze flag on failure.
- Per-store retention (log_retention_days_*) with expiry cleanup folded
  into the daily system_cleanup task; legacy database_auto_cleanup_* and
  of_database_auto_cleanup decommissioned.
- goose migrations: 6 log tables in PG (2 monthly-partitioned) + SQLite,
  retention config seeds, schedule cleanup; GET
  /api/v1/admin/status/log-database endpoint; frontend retention settings,
  switch-task UI and status badge; changelog and docs updated.

docs(plan): log database decoupling implementation plan

docs(design): log database decoupling design (ClickHouse optional)

internal/repository/logstore/clickhouse_store_test.go

@@ -0,0 +1,40 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package logstore
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+
+	db "github.com/Rain-kl/Wavelet/internal/infra/persistence"
+)
+
+// TestClickHouseHourlyDelegationRegression 验证 CH 后端小时级聚合读委托 analyticsrepo：
+// 未初始化 CH 连接时返回 analyticsrepo 的 "clickhouse connection is not initialized" 错误
+// （而非未实现/panic），证明 3 个方法都路由到 CH 原生查询。
+func TestClickHouseHourlyDelegationRegression(t *testing.T) {
+	if db.ChConnReady() {
+		t.Skip("clickhouse connection initialized; skipping delegation regression")
+	}
+	s := newClickHouseStore()
+	ctx := context.Background()
+	now := time.Now()
+	check := func(name string, err error) {
+		t.Helper()
+		if err == nil {
+			t.Fatalf("%s: want clickhouse-not-initialized error, got nil", name)
+		}
+		if !strings.Contains(err.Error(), "clickhouse connection is not initialized") {
+			t.Fatalf("%s: unexpected error %v", name, err)
+		}
+	}
+	_, err := s.ListTrafficHourly(ctx, "n1", now)
+	check("ListTrafficHourly", err)
+	_, err = s.ListAccessLogHourly(ctx, "n1", now)
+	check("ListAccessLogHourly", err)
+	_, err = s.ListMetricHourly(ctx, "n1", now)
+	check("ListMetricHourly", err)
+}