Fix Flatpak missing locale support (#12714)

Add the localization/ directory to the Flatpak source list so
run_gettext.sh can compile .po files into .mo translations.

Replace LC_ALL=C.UTF-8 with LC_NUMERIC=C in the entrypoint script
to preserve the user's language settings while still preventing
decimal-separator parsing issues.

scripts/flatpak/entrypoint

@@ -4,6 +4,8 @@
 grep -q org.freedesktop.Platform.GL.nvidia /.flatpak-info && export WEBKIT_DISABLE_DMABUF_RENDERER=1
 
 # Work-around https://github.com/bambulab/BambuStudio/issues/3440
-export LC_ALL=C.UTF-8
+# Use LC_NUMERIC instead of LC_ALL to prevent decimal separator issues
+# while preserving the user's language/locale for translations.
+export LC_NUMERIC=C
 
 exec /app/bin/orca-slicer "$@"

scripts/flatpak/io.github.orcaslicer.OrcaSlicer.yml

@@ -347,6 +347,9 @@ modules:
       - type: dir
         path: ../../src
         dest: src
+      - type: dir
+        path: ../../localization
+        dest: localization
 
       - type: file
         path: ../../CMakeLists.txt