Add recentchange SSE ingest service with Postgres persistence and replay tool

[artvandelay]

Motivation

• Implement a long-running ingest service to reliably consume the Wikimedia recentchange SSE stream with resume/reconnect semantics for gap-free ingestion.
• Filter events at ingest time to focus on enwiki and configured namespaces while dropping bot/minor edits to reduce noise.
• Persist raw events durably for backfills and analysis and expose simple metrics for throughput, reconnects, and lag.
• Provide a replay tool to reprocess stored events for backfills and testing.

Description

• Add services/ingest/recentchange_ingest.py which parses the SSE stream, honors Last-Event-ID for resume, implements exponential backoff reconnects, filters events, logs structured JSON metrics, and writes events to the recentchange_events Postgres table.
• Implement RecentChangeStore with automatic table/index creation and insert_event/fetch_last_event_id helpers to support idempotent inserts and resume.
• Add scripts/replay_recentchange.py CLI to stream stored events from the DB (by id range/limit) and emit JSON lines for replay/backfill workflows, and add services/ingest/__init__.py.
• Add psycopg2-binary to pyproject.toml and require POSTGRES_DSN (env/arg) for DB connectivity.

Testing

• No automated tests were executed as part of this change.

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Codex Task