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/apps/admin/system_config/routers_test.go

@@ -27,7 +27,7 @@ import (
 	"github.com/Rain-kl/Wavelet/internal/shared/response"
 )
 
-const expectedDefaultConfigsCount = 34
+const expectedDefaultConfigsCount = 37
 
 func setupTestRouter(authUser *model.User) *gin.Engine {
 	r := testhelper.NewTestGinEngine()
@@ -168,8 +168,8 @@ func TestListSystemConfigs(t *testing.T) {
 		var configs []model.SystemConfig
 		_ = json.Unmarshal(dataBytes, &configs)
 
-		if len(configs) != 5 {
-			t.Errorf("expected 5 business configs, got %d: %v", len(configs), configs)
+		if len(configs) != 8 {
+			t.Errorf("expected 8 business configs, got %d: %v", len(configs), configs)
 		}
 	})
 }