Add async function support to profile decorator

[valentinstn]

Summary

• `@profile()` now works on `async def` functions by detecting coroutine functions via `asyncio.iscoroutinefunction`
• The async wrapper uses `await` so the event loop is not blocked
• No change to sync function behavior or context manager mode

Test plan

• `@profile(open_flamechart=False)` on an `async def` function produces a `.prof` file
• Sync decorator behavior is unchanged