FLEX pager app (#2883)

* Add FLEX pager support

- Introduced a new FLEX configuration function in baseband_api.
- Added FLEX application view and associated UI elements.
- Implemented FLEX processing logic in proc_flex, including demodulation and message handling.
- Updated CMakeLists to include new FLEX source files and headers.
- Enhanced message system to support FLEX-specific messages and statistics.

This commit lays the groundwork for FLEX pager functionality, allowing for the reception and processing of FLEX messages.

* Fixed baseband and moved app to external with some other fixes.

* Format code

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Co-authored-by: RocketGod <57732082+RocketGod-git@users.noreply.github.com>

firmware/application/external/external.cmake

@@ -264,6 +264,10 @@ set(EXTCPPSRC
 	#adult_toys_controller  144 bytes 
 	external/adult_toys_controller/main.cpp
 	external/adult_toys_controller/ui_adult_toys_controller.cpp
+
+	#flex_rx
+	external/flex_rx/main.cpp
+	external/flex_rx/ui_flex_rx.cpp	
 )
 
 set(EXTAPPLIST
@@ -330,4 +334,5 @@ set(EXTAPPLIST
 	bht_tx
 	morse_practice
 	adult_toys_controller
+	flex_rx
 )