add support for Winkeyer devices as CW keyer

[ftl]

Add support for the K1EL Winkeyer protocol as an additional CW keyer device type, alongside the existing cwdaemon (UDP) and radio keyers. Winkeyer is a serial-line CW processor used by WKUSB, WK3-based interfaces, and many integrated rig-control boxes (microHAM, etc.). Supporting it lets Hello Contest key a transmitter directly through a Winkeyer without cwdaemon in between.

Hello Contest will only use the device as CW keyer. All the necessary configuration must be done with an external tool.

An example keyer hardware configuration for a Winkeyer device:

"keyers": [
	{
		"name": "Winkeyer 1",
		"type": "winkeyer",
		"address": "/dev/ttyUSB0"
	}
]

The following commands will be used by Hello Contest:

Command	Bytes	Purpose
Open Host	<00>2	Enter the host mode
Close Host	<00>3	Leave the host mode
Set WPM Speed	<02><nn>	Speed(wpm). nn = 5–99 WPM. nn=0 → follow the hardware speed pot.
Clear Buffer	<0A>	Abort(). Resets input buffer, aborts a character mid-stream, cancels tune/pause.
(data bytes)	ASCII ≥ 0x20	Send(text).
Request Status	<15>	Query status byte (busy / breakin / buffer).

Meaning of the status byte:

Top 3 bits are always 110. WK1/WK2 mode bits:

• bit 4 WAIT — waiting on a timed event.
• bit 3 KEYDOWN — tune/key-down active (WK1 mode).
• bit 2 BUSY — keyer is actively sending Morse (1 = busy). This is how the
  driver knows when a Send has finished — relevant for parrot / sequential
  sends.
• bit 1 BREAKIN — paddle break-in active (operator touched the paddle;
  clears the serial buffer).
• bit 0 XOFF — input buffer > 2/3 full; host should stop sending data (flow
  control).

Unsolicited speed-pot bytes have top bits 10 and carry a 6-bit WPM offset.

References:

• WK3 datasheet v1.3: https://www.hamcrafters2.com/files/WK3_Datasheet_v1.3.pdf
• WK2 datasheet v23: https://hamcrafters2.com/files/WK2_Datasheet_v23.pdf
• K1EL: https://www.k1elsystems.com/WK3IC.html