Make Ogg, Opus, and video file transcription reliable

[joshtech90]

Summary

• normalize Ogg/Opus inputs to a temporary mono 16 kHz MP3 before upload
• extract only the audio track from supported video containers
• keep original files untouched and remove temporary files after each request
• expose the tray action as Audio/Video File(s) and preserve multi-file clipboard output
• improve upload timeout handling for larger media files
• document the FFmpeg path and media workflow on macOS

Verification

• ruff check app tests run.py
• mypy app/core app/services app/audio app/hotkeys app/ui
• 138 pytest tests
• real .ogg and .opus files from the macOS Desktop both normalized and transcribed successfully
• generated video audio-extraction coverage
• original media files remained unchanged