bwrap: Can't mkdir parents for /app/share/runtime/locale: Read-only file system

Even without io.github.amit9838.mousam.Locale installed, the app fails to start and shows the following error:

text
bwrap: Can't mkdir parents for /app/share/runtime/locale: Read-only file system

Reproduction steps:

Install Mousam:
```
flatpak install flathub io.github.amit9838.mousam
```
Start it:
```
flatpak run io.github.amit9838.mousam
```
The error appears immediately.

What I tried:

Verified my filesystem is writable (mount shows rw, dmesg has no read-only entries).

Removed and reinstalled both the app and all related runtimes.

Even without the Locale extension, the same bwrap message appears.

Expected behavior:
The app should start normally or fall back to English without any locale errors.

Additional note:
I’m running LMDE 7 (based on Debian 13 Trixie). It uses Flatpak 1.14.x from the upstream Debian repository. The issue occurs regardless of the Locale extension being installed, which suggests that the problem is caused by the app’s main Flatpak sandbox configuration or incompatible mount rules with the new Flatpak/bubblewrap runtime on Debian 13.

Notes:
This issue may indicate that the main Flatpak package is missing its Locale integration setup or contains an incorrectly configured mount point.

Reproduce the failure with `flatpak run io.github.amit9838.mousam` on LMDE 7 and inspect the app's main Flatpak sandbox configuration, especially the `/app/share/runtime/locale` mount setup. Done means the application starts successfully without the bubblewrap read-only filesystem error, including when the Locale extension is absent.

Written by the indexing model from the issue text.