feat: Add mod build environment with version + git hash

Add `env:mod` PlatformIO environment that sets CROSSPOINT_VERSION to
"{version}-mod+{git_hash}" via a pre-build script. Usage: `pio run -e mod -t upload`

Co-authored-by: Cursor <cursoragent@cursor.com>

platformio.ini

@@ -55,6 +55,14 @@ build_flags =
   ${base.build_flags}
   -DCROSSPOINT_VERSION=\"${crosspoint.version}-dev\"
 
+[env:mod]
+extends = base
+extra_scripts =
+  ${base.extra_scripts}
+  pre:scripts/inject_mod_version.py
+build_flags =
+  ${base.build_flags}
+
 [env:gh_release]
 extends = base
 build_flags =