Feature Request: Add Async Setup Support

[ppinklesh]

Add an option in the project creation flow to enable async setup.
During the CLI prompts, users should be asked whether they want to generate a project with async support or the regular sync setup.
By default, the project should remain synchronous, but users can opt-in for async when prompted.

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Expected Behavior

When running:

fastapi-create-project

The CLI should include a prompt like:

Do you want to use async setup? (y/N):

If the user selects yes, generate the project using:

• sqlalchemy.ext.asyncio (create_async_engine, AsyncSession, async_sessionmaker)
• Async-compatible database drivers (asyncpg, aiosqlite)
• Async CRUD operations and routes using async def and await

If the user selects no, generate the current synchronous setup.

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Implementation Notes

• Add a new prompt in the CLI workflow (questionary / click / whichever CLI library used).
• Introduce a flag internally (e.g. use_async=True|False).
• Adjust database and CRUD templates accordingly.
• Update dependencies to install async drivers only if async setup is chosen.
• Update README and generated project docs.

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Acceptance Criteria

• CLI prompts user whether to enable async setup.
• Default behavior remains synchronous (if user presses Enter).
• Async setup scaffolds correctly when chosen.
• Async drivers installed conditionally.
• Documentation updated.