feat: use DateTime abstraction from apalis-sql (#30)

Replace direct chrono dependency with DateTime/DateTimeExt from apalis-sql,
enabling support for both chrono and time datetime libraries via feature flags.

Changes:
- Add `chrono` (default) and `time` feature flags
- Use DateTimeExt::from_unix_timestamp instead of chrono::Utc.timestamp_opt
- Update apalis dependencies to 0.7.0-rc.2
- Move chrono to dev-dependencies (only needed for tests/examples)

Related: apalis-dev/apalis#655

Author: Himmelschmidt

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- feat: use DateTime abstraction from apalis-sql
+- bump: update apalis deps to rc.2
 - bump: to v1.0.0-rc.1 (#28)
 
 ## [1.0.0-beta.4] - 2025-12-08