Add the ITPROTECH MK series (8808) as a third pad family

Confirmed on the MK-09 (8808:660a, 9 keys): the vendor's .NET configurator
was decompiled for the wire format and every frame was then written to a
real pad and read back. Keys, media keys and multikey sequences are
supported; lighting from the command line.

The firmware acts on every other output report, so each report is sent
twice (as the vendor software does) and every write is verified by reading
the key back. The app now keeps one state file per pad and starts with a
known layout for a known USB id, and the editor asks the backend whether a
binding fits before offering to write it. The actions listener and the
udev rule cover every supported vendor.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/adding-a-pad.md

@@ -26,6 +26,8 @@ A pad from a different family fails one of those, and the app leaves it alone ra
 
 The pad reports how many keys and knobs it has, but not how they're arranged, so the first guess at rows and columns may be wrong. Fix it with [Edit layout](#-if-the-drawing-doesnt-match-your-pad) and the drawing will match your hardware.
 
+The same button works for the ITPROTECH pads (vendor id `8808`): the app asks the pad for its key records and adopts it if they come back cleanly.
+
 ## If it doesn't answer
 
 Some pads in this family speak an older protocol and won't answer. Working those out needs a capture of the vendor software, the same process used for this one. You'll need `MINI_KEYBOARD.exe` and Wine.