feat: add performance logging for ingestion phases and GeoIP lookups

[fukusuket]

Closed #14

[Copilot]

Pull request overview

This PR adds optional ingestion performance instrumentation to the Rust ingester so operators can see where time is spent (discovery, dedup-map load, parsing, insertion, GeoIP, batch marking) and estimate throughput.

Changes:

• Add --perf-log flag to ingester ingest and print a perf breakdown to stderr on completion.
• Track per-phase timings in IngestStats via a new PhaseTimings struct.
• Time GeoIP lookups during insertion and surface that timing to the ingestion pipeline.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 7 comments.

File	Description
ingester/src/main.rs	Adds --perf-log CLI flag and prints perf breakdown/throughput when enabled.
ingester/src/ingest.rs	Introduces PhaseTimings and instruments discovery/dedup/parse/recv-wait/insert/batch-mark.
ingester/src/db.rs	Times GeoIP lookups during inserts and returns (rows_inserted, geoip_ns) from insert_events_with_geo.