fix: add missing methods to QueueInterface and improve type declarations

[michalsn]

Description
This PR fixes static analyzer errors by properly declaring all public API methods in QueueInterface and JobInterface.

• Added missing methods to QueueInterface: setDelay(), setPriority(), chain()
• Added complete return types to all interface methods
• Made BaseHandler and BaseJob implement their respective interfaces
• Removed redundant interface declarations from child classes
• Updated generator template and docs

Fixes #74

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide