v0.1.2

Cleanup & performance

• Startup ~1.2s faster — lazy-import mediapipe and cv2
• ~18 MB/s less GC pressure — removed unnecessary frame copies in camera hub
• ~20 MB freed on stop — MediaPipe landmarker properly closed
• Bug fix — smoothing window now cleared on recalibration
• D-Bus cleanup — screen lock observer properly disconnects on quit
• Dead code removed — PauseReason, dead_zone, blur_when_away, unused _today_key
• Code quality — centralized constants, deduplicated overlay drawing, ruff 0 errors
• PyPI description — dedicated README for the PyPI listing