fix: Updates type annotations to use Optional instead of union syntax

[dorel14]

Changes type annotations for the scheduler parameter from union syntax (AsyncIOScheduler | None) to the Optional generic type for consistency across the codebase. Also adds Optional to the typing imports.

[gemini-code-assist]

Code Review

This pull request modifies taskiq_flow/scheduling/scheduler.py to replace the union type hint AsyncIOScheduler | None with Optional[AsyncIOScheduler]. The reviewer suggests using from __future__ import annotations instead, which allows keeping the cleaner AsyncIOScheduler | None syntax, avoids runtime errors when apscheduler is not installed, and maintains consistency with the rest of the codebase.

[gemini-code-assist]

By adding from __future__ import annotations at the very top of this file, we can avoid importing Optional entirely and keep the imports clean.

Suggested change

	from typing import Any, Optional, cast
	from typing import Any, cast

[gemini-code-assist]

Instead of switching to Optional[AsyncIOScheduler] and introducing inconsistency with the rest of the codebase (which consistently uses the | None union syntax, such as job_store_url: str | None on the next line), we can resolve the runtime TypeError (which occurs when apscheduler is not installed and AsyncIOScheduler is None) by adding from __future__ import annotations at the top of the file.

This postpones the evaluation of annotations, allowing us to safely use AsyncIOScheduler | None without runtime crashes.

Suggested change

	scheduler: Optional[AsyncIOScheduler] = None,
	scheduler: AsyncIOScheduler | None = None,