Make the outbox, scheduling locks and CI database-agnostic

[ancongui]

LaraFly's same-transaction outbox, scheduling locks and CI no longer depend on PostgreSQL alone.

What changes

• firefly/eda-database (firefly.eda.provider=database): the outbox on any Laravel connection. Rows are claimed by a lease committed before delivery, through an OutboxClaimStrategy chosen from the server version: SKIP LOCKED on PostgreSQL, MySQL 8.0.1+ and MariaDB 10.6+, READPAST on SQL Server, and a portable optimistic lease elsewhere (SQLite, unknown drivers). It can be overridden with firefly.eda.database.claim-strategy.
• firefly/eda-postgres is now the database outbox plus pg_notify/LISTEN. The old classes and firefly.eda.postgres.* keys still work as deprecated subclasses and aliases. The outbox table gains claimed_by / claimed_until (upgrade migration included).
• Durable dead letters for eda and messaging (...dead-letter.store=database), with replay commands.
• firefly/scheduling-database: lock.provider=database (a portable lease table) and lock.provider=mysql (GET_LOCK, MySQL and MariaDB).
• CI:
  • an integration job matrix over PostgreSQL 16, MySQL 8.4, MariaDB 11 and SQL Server 2022;
  • a brokers job for RabbitMQ, Kafka and Redis;
  • composer test:integration and docker-compose.integration.yml to run the same lanes locally.
• Data layer on real servers: exception translation, statement timeouts (including a new SQL Server LOCK_TIMEOUT branch), and pessimistic/optimistic locking.
• Docs: README, index, the module pages and diagrams no longer present PostgreSQL as the only atomic outbox. New pages: eda-database, scheduling-database, integration-testing and a database support matrix.

Fixed

• Concurrent consumers could deliver an outbox row twice. The Postgres consumer's FOR UPDATE SKIP LOCKED lock ended with its statement, and on other drivers the claim was an unlocked read. Two racing processes are now integration-tested to deliver every row exactly once on each server.
• The RabbitMQ round trip against a real broker, and the samples/lumen integration test that called a non-existent firefly:eda:consume command.
• IntegrationDsn never echoes a DSN (and its password) in errors, validates SQL Server certificates by default, creates SQLite test files in a private 0700 directory, and does not let a URL query override host or credentials.

Verification

• composer check (Pint, PHPStan max, Pest, Deptrac): exit 0, 5877 tests passed.
• pest --group integration against real PostgreSQL 16, MySQL 8.4, MariaDB 11, RabbitMQ, Kafka and Redis: 124 passed, 0 failed. The 16 skips are SQL Server tests, which run only in the new CI lane because there is no arm64 image locally.