Claim only delivery types supported by each worker

[endrju19]

Summary

Workers now claim only PENDING entries for their registered delivery types. The processor rotates its starting type and uses at most two claim queries per batch, independent of the number of types: one for the starting type and, when needed, one IN query for the rest. A mismatched entry is also rejected before delivery.

PostgreSQL gets a partial (delivery_type, created_at, id) WHERE status = 'PENDING' index; MySQL gets (status, delivery_type, created_at, id) plus an exact, binary type check for case-insensitive collations. The unrestricted OutboxStore.claimPending(limit) remains available to direct callers and keeps its existing index. Custom stores used by Okapi's processor must implement RouteAwareOutboxStore; Spring autoconfiguration rejects an unsafe store at startup.

Verification

• After resolving conflicts with main, ./gradlew build ktlintCheck passed locally, covering all modules and database, HTTP, Kafka and Spring Boot tests.
• The HTTP batch concurrency test now uses a server-side request barrier. Every request must arrive before any successful response is sent; intentionally switching delivery to sequential makes the test fail. Both PR Claim only delivery types supported by each worker #120 and chore(deps): bump the production group with 8 updates #121 include the same test fix.
• Core, Spring Boot and integration tests passed locally on PostgreSQL and MySQL Docker containers, including migrations, concurrent heterogeneous workers, exact type matching, HTTP and Kafka. ktlintCheck passed.
• On a 1,000,000-row outbox with 900,000 older unsupported rows, a 100-type absent IN claim used the route index and took about 0.16 ms on PostgreSQL and 0.21 ms on MySQL in local measurements. The previous full PostgreSQL index produced a 165 ms scan for that case. Scripts and context are in benchmarks/route-aware-claim/.
• There is a write cost from the additional index. In exploratory repeated local runs, PostgreSQL insert/update medians were 1.47×/1.07× versus the legacy index alone; MySQL medians were 1.18×/1.29×. These are workload-specific measurements, not throughput guarantees.

Rollout

The branch includes the current main, preserving #119 startup validation and #115 outbox-id headers. For manually managed schemas, the README links both migrations: apply 001 and 002 in order for a new installation, or apply 002 before starting updated workers on an existing schema. Run PostgreSQL migration 002 outside a transaction because it creates the index concurrently. Older workers can still claim unsupported types, so publish a new type only after all old processors are upgraded or stopped. Previously FAILED rows need separate recovery.

Closes #116