Implement threading, logging, and CJK font support

Major improvements to GUI stability and internationalization:

- Fix GUI freezing by implementing threaded audio analysis
  - Add AudioAnalysisWorker thread for background processing
  - Progress signals with percentage updates
  - Thread-safe communication via Qt signals

- Add comprehensive CLI logging system
  - 5 log levels: ERROR, WARN, INFO, DEBUG, TRACE
  - Command line control: --log-level, --log-file
  - Real-time feedback during analysis operations

- Implement CJK font fallback system
  - FontManager with 3-tier fallback (custom → system → default)
  - Cross-platform CJK font detection (Windows/macOS/Linux)
  - Licensing-safe fonts/ directory with gitignored font files
  - Setup utility and comprehensive documentation

- Fix numpy array formatting issue with BPM detection
- Add progress indicators for long-running operations
- Preserve fonts directory structure with placeholder file

🤖 Generated with [Claude Code](https://claude.ai/code)

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

fonts/PLACE_YOUR_FONT_FILES_HERE

@@ -0,0 +1,12 @@
+This directory is for custom CJK fonts to improve character rendering.
+
+Supported formats: .ttf, .otf, .ttc
+
+Recommended free fonts for CJK support:
+- Noto Sans CJK (Google Fonts)
+- Source Han Sans (Adobe)
+
+The application will automatically detect and use fonts placed here.
+For setup instructions, run: python setup_fonts.py
+
+Note: Only add fonts you have proper licensing rights to distribute.