perf(clickhouse): Phase 2 legacy governance — TTL cleanup, unified pool, MV, ops API

- Replace retention ALTER DELETE with MATERIALIZE TTL; use TRUNCATE for delete-all
- Remove GORM ClickHouse pool; migrate user access log reads to ChConn
- Drop query-side trim(remote_addr); enable wait_for_async_insert=1
- Add of_node_traffic_hourly MV and dashboard traffic trend fallback
- Add GET /admin/status/clickhouse operational metrics endpoint

internal/repository/analytics/clickhouse_maintenance.go

@@ -0,0 +1,74 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package analytics
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"
+)
+
+const (
+	// CleanupModeTTLMaterialize expires rows via table TTL instead of ALTER DELETE mutations.
+	CleanupModeTTLMaterialize = "ttl_materialize"
+	// CleanupModeTruncate removes all rows via TRUNCATE TABLE.
+	CleanupModeTruncate = "truncate"
+)
+
+// CleanupOutcome describes a non-mutation ClickHouse cleanup operation.
+type CleanupOutcome struct {
+	EligibleCount int64
+	Mode          string
+}
+
+func countClickHouseRows(ctx context.Context, conn driver.Conn, countSQL string, countArgs []any) (int64, error) {
+	var count uint64
+	if err := conn.QueryRow(ctx, countSQL, countArgs...).Scan(&count); err != nil {
+		return 0, fmt.Errorf("count clickhouse rows: %w", err)
+	}
+	return safeInt64Count(count), nil
+}
+
+func materializeTableTTL(ctx context.Context, conn driver.Conn, tableName string) error {
+	sql := fmt.Sprintf("ALTER TABLE %s MATERIALIZE TTL", tableName)
+	if err := conn.Exec(ctx, sql); err != nil {
+		return fmt.Errorf("materialize ttl on %s: %w", tableName, err)
+	}
+	return nil
+}
+
+func expireRowsViaTTL(ctx context.Context, conn driver.Conn, tableName string, countSQL string, countArgs []any) (CleanupOutcome, error) {
+	count, err := countClickHouseRows(ctx, conn, countSQL, countArgs)
+	if err != nil {
+		return CleanupOutcome{}, err
+	}
+	if count == 0 {
+		return CleanupOutcome{Mode: CleanupModeTTLMaterialize}, nil
+	}
+	if err := materializeTableTTL(ctx, conn, tableName); err != nil {
+		return CleanupOutcome{}, err
+	}
+	return CleanupOutcome{
+		EligibleCount: count,
+		Mode:          CleanupModeTTLMaterialize,
+	}, nil
+}
+
+func truncateClickHouseTable(ctx context.Context, conn driver.Conn, tableName string) (CleanupOutcome, error) {
+	count, err := countClickHouseRows(ctx, conn, "SELECT count() FROM "+tableName, nil)
+	if err != nil {
+		return CleanupOutcome{}, err
+	}
+	if count == 0 {
+		return CleanupOutcome{Mode: CleanupModeTruncate}, nil
+	}
+	if err := conn.Exec(ctx, "TRUNCATE TABLE "+tableName); err != nil {
+		return CleanupOutcome{}, fmt.Errorf("truncate %s: %w", tableName, err)
+	}
+	return CleanupOutcome{
+		EligibleCount: count,
+		Mode:          CleanupModeTruncate,
+	}, nil
+}