Replace ClickHouse metrics storage with TimescaleDB

[Copilot]

Migrates Holotable’s metrics backend from ClickHouse to TimescaleDB while preserving guarded dashboard queries, catalog introspection, and read-only access.

Changes

• Metrics runtime

  • Replaced the ClickHouse client with PostgreSQL execution in read-only transactions.
  • Migrated catalog discovery to information_schema.columns.
  • Updated bound time-range parameters and PostgreSQL-specific SQL safety controls.

• TimescaleDB infrastructure

  • Added the http_requests hypertable, one-minute continuous aggregate, and seven-day retention policy.
  • Added restricted metrics-role provisioning.
  • Replaced the ClickHouse container and initialization scripts with TimescaleDB.

• Application integration

  • Migrated source configuration, demo data, SQL generation guidance, and UI defaults.
  • Reworked the metrics seeder for PostgreSQL batch inserts.
  • Removed @clickhouse/client and updated documentation and tests.

SELECT time_bucket('1 minute', ts) AS minute,
       count(*) AS requests
FROM http_requests
GROUP BY minute
ORDER BY minute;