Add structured public DataProvider exceptions

[remdui]

What changed

• adds a public unchecked DataProviderException hierarchy with stable error codes
• exposes backend type, logical connection identifier, operation name, retry advice, execution outcome, immutable diagnostics and a validated correlation ID
• adds structured failures for configuration, registration, unavailable/disabled backends, authentication, generic operation failure, timeout, queue/subscription saturation, serialization, conflict, transactions and closed providers
• adds strict registerDatabaseOrThrow(...) and requireRegisteredDatabase(...) methods to default and scoped APIs
• maps MySQL, MongoDB, Redis, messaging and execution-runtime failures at public async boundaries
• preserves transaction phase, uncertain commit outcomes and suppressed rollback/cleanup failures
• redacts public backend causes and diagnostic data

Compatibility

• existing nullable and optional registration methods keep their current return behavior
• existing legacy lifecycle methods retain their previous IllegalStateException behavior after closure
• new strict methods report closure through ProviderClosedException
• normal caller validation failures remain standard validation exceptions rather than being mislabeled as backend outages
• public API method signatures remain source-compatible

Final engineering review

• unknown SQL/driver failures now use DataProviderOperationException instead of incorrectly reporting backend unavailability
• general exception unwrapping is limited to actual async wrappers; registration-only lifecycle wrappers are handled separately
• read timeouts are SAFE with NOT_APPLIED; write timeouts remain CONDITIONAL with MAY_HAVE_APPLIED
• transaction setup always closes an acquired connection when initialization fails
• transaction cleanup is explicit rather than relying on try-with-resources suppression
• public rollback, restore and close failures remain structured and redacted
• post-commit restore/close failures use phase CLEANUP, outcome MAY_HAVE_APPLIED, and are non-retryable
• JVM-fatal errors remain primary and are never converted into ordinary DataProvider failures
• validates diagnostic correlation identifiers and diagnostic metadata
• improves CI failure diagnostics by printing and uploading Surefire and Failsafe reports without masking the original result
• documents strict/legacy behavior, generic failures, retry safety, commit uncertainty, cleanup semantics and redaction guarantees

Validation

• CI Lint: passed
• complete JDK 25 unit test suite: passed
• MySQL Testcontainers integration tests: passed
• MongoDB Testcontainers integration tests: passed
• Redis Testcontainers integration tests: passed
• final validated head: 2627abb43f27e0281358d207728707a2afe2b62c