Migrate risk_control audit logs to internal/db/batchwriter and add
openflare/chwriter with per-table async flush for observability
timeseries and node access logs.
Replace single-row ClickHouse inserts and pre-insert SELECT count()
dedup with repository BatchInsert* APIs, in-process TTL dedup for
metric/report snapshots, and bootstrap initialization on API startup.
Introduce internal/db/batchwriter as a reusable generic buffered writer
for per-domain ClickHouse flush pipelines, with unit tests and default
batch tuning aligned with audit log ingestion.
Add clickhouse-batchwriter agent skill and cross-references in AGENTS.md
and database-migration. Business layers are not wired yet.
ryan