Introduce HW camera stack using Rockchip MPP/VPU

[paxx12]

Summary

This branch introduces an extended firmware variant with a new hardware-accelerated camera stack for the Snapmaker U1, using the Rockchip MPP/VPU.

It only works in LAN mode, as it does not support any cloud functions.

Key Changes

Uses https://github.com/paxx12/v4l2-mpp that follows a multi-process architecture:

• Custom V4L2 capture tool with Rockchip MPP hardware encoding
• Multi-process architecture:
  • capture-mipi-mpp (C) - captures MIPI video, encodes to H264/JPEG via hardware, exposes via sockets
  • capture-usb-mpp (C) - captures USB video, encodes to H264/JPEG via hardware, exposes via sockets
  • stream-http.py - HTTP server for camera endpoints
  • stream-mqtt.py - MQTT interface for timelapse generation (Snapmaker U1 compatible)

Camera Endpoints

Endpoint	Description
/webcam/snapshot.jpg	JPEG snapshot
/webcam/stream.mjpg	MJPEG stream (~15fps)
/webcam/stream.h264	H264 raw stream
/webcam/player	H264 web player

Firmware Variants

• Basic - SSH, USB ethernet, native camera (~1Hz in Fluidd)
• Extended - Basic + new HW-accelerated camera stack

Build System

• Renamed create_custom_firmware.sh → create_firmware.sh
• Reorganized overlays into basic/ and camera-new/ directories
• Updated GitHub Actions to build both firmware variants