feat: ✨ Input type is now optional for HandlerDecorator

[remimd]

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[Copilot]

Pull Request Overview

This PR makes the input type parameter optional for HandlerDecorator, allowing handlers to be registered without explicitly specifying the input type. The decorator now automatically infers the input type from the handler's handle method signature.

• Input type parameter is now optional for all handler decorators (@command_handler, @event_handler, @query_handler)
• Automatic type inference from handler method signatures when input type is not provided
• Updated documentation and examples to demonstrate the new simplified syntax

Reviewed Changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_command_bus.py	Updated test to use new decorator syntax without explicit type parameters
tests/core/test_handler.py	Added comprehensive test coverage for HandlerDecorator functionality
documentation/writing-application-layer.md	Updated examples to show new simplified decorator syntax
documentation/fastapi-example.md	Updated FastAPI integration example with new decorator syntax
cq/middlewares/scope.py	Refactored to use dataclass and added exist_ok parameter for scope handling
cq/middlewares/retry.py	Changed parameter type from Iterable to Sequence for better type safety
cq/_core/scope.py	Renamed scope from ON_COMMAND to TRANSACTION
cq/_core/related_events.py	Added bool method and updated scope reference
cq/_core/message.py	Updated to use new TRANSACTION scope with exist_ok parameter
cq/_core/handler.py	Implemented new HandlerDecorator logic with automatic type inference

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