Notifications: Use libnotify

Use libnotify for meshtasticd desktop notifications.

Add "HAS_LIBNOTIFY" macro to guard for builds where libnotify is expected.
This is not included in buildroot/openwrt builds. (no libnotify except when extra repos are added).

Install desktop icon in the correct location on Debian and Fedora packages.
Update dependencies in packaging and dockerfiles.

variants/native/portduino/platformio.ini

@@ -2,6 +2,8 @@
 extends = portduino_base
 build_flags = ${portduino_base.build_flags} -I variants/native/portduino
   -I /usr/include
+  !pkg-config --cflags --libs libnotify
+  -D HAS_LIBNOTIFY=1
 board = cross_platform
 board_level = extra
 lib_deps = 
@@ -27,7 +29,8 @@ build_type = release
 lib_deps =
   ${native_base.lib_deps}
   ${device-ui_base.lib_deps}
-build_flags = ${native_base.build_flags} -Os -lX11 -linput -lxkbcommon -ffunction-sections -fdata-sections -Wl,--gc-sections
+build_flags = ${native_base.build_flags}
+  -Os -lX11 -linput -lxkbcommon -ffunction-sections -fdata-sections -Wl,--gc-sections
   -D RAM_SIZE=16384
   -D USE_X11=1
   -D HAS_TFT=1
@@ -55,7 +58,8 @@ build_type = release
 lib_deps =
   ${native_base.lib_deps}
   ${device-ui_base.lib_deps}
-build_flags = ${native_base.build_flags} -Os -ffunction-sections -fdata-sections -Wl,--gc-sections
+build_flags = ${native_base.build_flags}
+  -Os -ffunction-sections -fdata-sections -Wl,--gc-sections
   -D RAM_SIZE=8192
   -D USE_FRAMEBUFFER=1
   -D LV_COLOR_DEPTH=32
@@ -84,7 +88,8 @@ build_type = debug
 lib_deps =
   ${native_base.lib_deps}
   ${device-ui_base.lib_deps}
-build_flags = ${native_base.build_flags} -O0 -fsanitize=address -lX11 -linput -lxkbcommon
+build_flags = ${native_base.build_flags}
+  -O0 -fsanitize=address -lX11 -linput -lxkbcommon
   -D DEBUG_HEAP
   -D RAM_SIZE=16384
   -D USE_X11=1
@@ -112,7 +117,9 @@ build_src_filter = ${env:native-tft.build_src_filter}
 
 [env:coverage]
 extends = env:native
-build_flags = -lgcov --coverage -fprofile-abs-path -fsanitize=address ${env:native.build_flags}
+build_flags =
+  -lgcov --coverage -fprofile-abs-path -fsanitize=address
+  ${env:native.build_flags}
 ; https://docs.platformio.org/en/latest/projectconf/sections/env/options/test/test_testing_command.html
 test_testing_command =
   ${platformio.build_dir}/${this.__env__}/meshtasticd