Major update: bundled whisper-cli, model downloader, progress indicator

Features:
- whisper-cli and dependencies bundled in app (no brew required for users)
- Built-in model downloader with 5 model options (Tiny to Large)
- Download progress indicator (e.g., "45% Downloading Small")
- Model selection dropdown in Settings
- First-run wizard for initial model download

Security fixes:
- Input validation for language and model path
- Private temp directory for audio files
- Auto-cleanup of audio files after transcription
- Auto-detect whisper-cli path (ARM/Intel)

Bug fixes:
- Fixed Settings window crash (NSWindowController)
- Fixed model selection with tag-based indexing

Build:
- bundle-whisper.sh script for packaging whisper-cli
- Updated Makefile with Frameworks bundling

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,8 @@
 # Build
 macos/build/
 macos/WhisperDictate.app/Contents/MacOS/
+macos/WhisperDictate.app/Contents/Frameworks/
+macos/WhisperDictate.app/Contents/_CodeSignature/
 WhisperDictate
 *.o
 *.dSYM/