Restore internal camera support on firmware 1.3.5.x

[nerdoc]

Disclaimer: this PR is created by Claude Opus 5. It works as fix in my setup - but YMMV.
However - anything is better than the current state: the camree is not working any more with the last update.
And the script seems to be unmaintained - so... If noone does anything, it will die.

Problem

Since firmware 1.3.5.x the internal camera is owned exclusively by cam_app, which
publishes JPEG frames over a memfd IPC channel instead of exposing the UVC device.
input_uvc.so fails on it. The firmware update also wipes /etc/init.d, so nothing
listens on port 8080 anymore — while the nginx config installed by this script still
proxies /webcam/ to 127.0.0.1:8080. Only the producer is missing.

Reported in discussion
#901 (K1C and
K1 Max), and the workaround this PR is based on comes from there — credit to @laffsj.

Changes

1. New "Internal Camera Support" entry (K1 menu, option 19)

Installs S59mjpg_streamer, which runs mjpg_streamer with input_memfd.so. Both the
binary and the plugin ship with the firmware, so no Entware packages are needed. The
service waits for cam_app in a backgrounded subshell, so a slow camera init does not
stall the boot — rcS runs init scripts sequentially, and a foreground wait loop delays
everything after it.

Install is refused when USB Camera Support is present (both want port 8080) or when
input_memfd.so is missing (firmware too old).

2. S50usb_camera-single: recognize CCX2F3299

The guard only matched CCX2F3298, so the newer revision is treated as a third-party
USB camera. On my K1 the internal camera enumerates over USB, so it lands in V4L_DEVS
and the guard does not fire:

V4L_DEVS=[/dev/video4]
CREALITY_CAMS=0        # with 'CCX2F3298'
CREALITY_CAMS=2        # with 'CCX2F329[89]'

install_menu_K1.sh already checks for CCX2F3299, so this only brings the service in
line with the menu.

Testing

Tested on a K1, firmware build 2026-06-25, camera CCX2F3299 (1.3):

• stream and snapshot work on :8080 and through nginx on /webcam/ (both 4408 and 4409)
• repeated start is idempotent — it does not spawn a second streamer
• the detection numbers above are measured on that machine

Not tested: the boot path (the printer was mid-print), and hardware other than the K1.

Known limitations, not addressed here

• S50usb_camera-dual starts input_uvc.so -d /dev/video4 for the internal camera, which
  cannot work on 1.3.5.x either. Fixing it properly means mixing input_memfd for the
  internal camera with input_uvc for the USB one, and I have no dual-camera setup to
  test that on, so I left it alone.
• camera_settings_control.sh picks the nebula config (ranges 50…160) only for
  CCX2F3298; CCX2F3299 falls through to the generic one (−64…64). That looks related
  to discussion #910,
  but on my printer v4l2-ctl -d /dev/video4 -l returns nothing at all under this
  firmware, so I could not verify which ranges are correct and did not touch it.