working and resolving issue #70 - add MJPEG video stream endpoint

[MoveFastAndBreakThings-dot]

What this does

Adds a live video stream from the drone camera to EMU, replacing the per-detection static image updates.

Changes

• emu.py — new /video HTTP endpoint serving MJPEG (multipart/x-mixed-replace). Browser displays it with a plain
  <img> tag, no JS needed. Existing /ws websocket unchanged.
• video_emu_stream.py — two new classes:
  • SharedFrameCamera — wraps any CameraProvider, captures at fixed fps, shares latest frame across multiple
    consumers without double-capturing
  • VideoEmuStreamer — pulls from SharedFrameCamera, JPEG-encodes, pushes to /video
• aruco_stream.py — ArucoEmuStreamer callback: draws bounding box on detection frame, saves to disk, sends path
  over existing WS (static image pipeline preserved for YOLO/analysis)
• analysis.py — subscriber callback signature updated to pass bounding_box alongside position
• samples/aruco_stream.py — demo wiring everything together