Real provider integration: aggregator gateway behind TravelProviderGateway (Phase 3)

[jckail]

Summary

The first real provider integration — replaces the simulated-only sync path with an HTTP loyalty-data aggregator adapter (the roadmap's "one adapter over a loyalty-data aggregator to cover the long tail"), activated by config and sitting behind the existing TravelProviderGateway port.

• HttpAggregatorTravelProviderGateway (core) — POSTs {providerId, membershipNumber, credential?} to {baseUrl}/v1/balance with bearer auth, validates the response, forwards a transient credential for one-time use (never persisted), and can be scoped to supportedProviderIds. Injectable fetch; 5 unit tests including composite precedence over the simulated gateway.
• Refactor — a shared buildTravelProviderGateway() factory composes the aggregator (when configured) ahead of the simulated fallback. The web and worker containers now use it instead of hand-composing, and dropped their direct Composite/Simulated imports — one place owns the gateway wiring.
• Config — AGGREGATOR_API_URL / AGGREGATOR_API_KEY (web + worker).
• Infra — opt-in AGGREGATOR_API_KEY Secrets Manager placeholder (-c enableAggregator=true) + AGGREGATOR_API_URL context on the web service and the 6-hourly sync task; secret ARN output. Default deploys unchanged.
• Docs — docs/integrations.md (aggregator section + factory), .env-example.

Open/closed at work: no use case, route, or schema changes — syncs just start returning real balances for covered providers, and balance history accumulates automatically.

Verification

• 128 tests pass (97 core incl. 5 new + 20 bot + 11 extension); typecheck + eslint clean.
• cdk synth clean both default (no aggregator) and -c enableAggregator=true (secret + env on web + sync task confirmed in the template).

🤖 Generated with Claude Code

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