feat: 支持macOS平台WhisperCpp的GPU加速

[A1nair]

• 在 whisper_cpp.py 中增加了对 macOS 的检测

[Copilot]

Pull request overview

This PR enables GPU acceleration support for WhisperCpp on macOS by conditionally applying the --no-gpu flag based on the platform.

Key Changes:

• Added sys module import for platform detection
• Modified _build_command to only add --no-gpu flag on non-macOS platforms (Windows/Linux)

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[Copilot]

The codebase already has a platform detection utility function is_macos() in app/core/utils/platform_utils.py that uses platform.system() == "Darwin". For consistency with the rest of the codebase, consider using that existing function instead of sys.platform != "darwin".

Suggested change:

if not is_macos():
    whisper_params.append("--no-gpu")

And add the import at the top:

from ..utils.platform_utils import is_macos