Add SAME TX external app (#3069)

* Add SAME TX external app

Adds a Specific Area Message Encoding (SAME/EAS) transmitter as an
external app (.ppma) for HackRF PortaPack.

SAME is the digital protocol used by NOAA Weather Radio and the
Emergency Alert System in the US and Canada for broadcasting
emergency alerts (tornado warnings, flash floods, EAN, etc.)
on 162.400-162.550 MHz and AM/FM broadcast stations.

Features:
- Originator code selector (WXR, EAS, CIV, PEP)
- Event code selector: 26 standard SAME event codes
  (RWT, TOR, SVR, FFW, EAN, etc.) with live name display
- FIPS location code entry (state 00-99 + county 000-999)
- Purge time entry (hours + minutes)
- Live message preview showing the encoded header
- AFSK encoding: mark=2083Hz, space=1563Hz, 520.833 baud
- FM deviation: 5 kHz, repeated 3x per SAME spec
- Default frequency: 162.550 MHz (WX channel 7)

Protocol details:
- 16-byte 0xAB preamble (bit-reversed for LSB-first AFSK)
- Header: ZCZC-ORG-EVT-SSPCCC+HHMM-JJJHHMM-STATION-
- Uses existing PAFT (proc_afsk) baseband image

* Apply clang-format via format-code.sh

* Add GPL license headers, guard re-entry, call set_transmitting(true)

- Add standard PortaPack GPL-2.0 license header to ui_same_tx.cpp and .hpp
- Guard start_tx() with tx_active_ to prevent re-entrant calls
- Call tx_view.set_transmitting(true) after starting TX so the
  TransmitterView button switches to stop mode

firmware/application/external/external.cmake

@@ -103,6 +103,10 @@ set(EXTCPPSRC
 	external/sstvtx/main.cpp
 	external/sstvtx/ui_sstvtx.cpp
 
+	#same_tx
+	external/same_tx/main.cpp
+	external/same_tx/ui_same_tx.cpp
+
 	#sstvrx
 	external/sstvrx/main.cpp
 	external/sstvrx/ui_sstvrx.cpp
@@ -343,6 +347,7 @@ set(EXTAPPLIST
 	adsbtx
 	#morse_tx
 	sstvtx
+	same_tx
 	sstvrx
 	random_password
 	acars_rx