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/analytics/node_access_log.go

@@ -15,10 +15,7 @@ import (
 )
 
 // NodeAccessLogRegionCount aggregates access log regions.
-type NodeAccessLogRegionCount struct {
-	Region string
-	Count  int64
-}
+type NodeAccessLogRegionCount = analyticsmodel.NodeAccessLogRegionCount
 
 func nodeAccessLogConn() (driver.Conn, error) {
 	if db.ChConn == nil {
@@ -151,28 +148,13 @@ ORDER BY count DESC, trimmed_region ASC`, tableName, clause)
 }
 
 // NodeAccessLogTrafficSummary is a window-level access log traffic summary.
-type NodeAccessLogTrafficSummary struct {
-	RequestCount  int64
-	ErrorCount    int64
-	UniqueIPCount int64
-	BytesSent     int64
-	RequestLength int64
-	NodeCount     int64
-}
+type NodeAccessLogTrafficSummary = analyticsmodel.NodeAccessLogTrafficSummary
 
 // NodeAccessLogValueCount is a grouped value count (status_code, host, ...).
-type NodeAccessLogValueCount struct {
-	Value string
-	Count int64
-}
+type NodeAccessLogValueCount = analyticsmodel.NodeAccessLogValueCount
 
 // NodeAccessLogNodeAggregate is per-node traffic over a window.
-type NodeAccessLogNodeAggregate struct {
-	NodeID        string
-	RequestCount  int64
-	ErrorCount    int64
-	UniqueIPCount int64
-}
+type NodeAccessLogNodeAggregate = analyticsmodel.NodeAccessLogNodeAggregate
 
 // TrafficSummaryNodeAccessLogs returns request/error/UV/bytes/node counts for the filter.
 func TrafficSummaryNodeAccessLogs(ctx context.Context, filter NodeAccessLogFilter) (NodeAccessLogTrafficSummary, error) {