Unable to build on RPI 500+ with Trixie RPI OS

```
Linking app Workspace ...
/usr/bin/ld: ./obj/Workspace.obj/Network/NetworkVolumeManager.m.o: in function `_i_NetworkVolumeManager__mountSFTPService_username_password_':
/Local/Users/jmaloney/Documents/gershwin-build/repos/gershwin-workspace/Workspace/Network/NetworkVolumeManager.m:530:(.text+0x1d74): undefined reference to `._OBJC_REF_CLASS_SFTPMount'
/usr/bin/ld: /Local/Users/jmaloney/Documents/gershwin-build/repos/gershwin-workspace/Workspace/Network/NetworkVolumeManager.m:530:(.text+0x1d78): undefined reference to `._OBJC_REF_CLASS_SFTPMount'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
gmake[5]: *** [/System/Library/Makefiles/Instance/application.make:131: Workspace.app/./Workspace] Error 1
gmake[4]: *** [/System/Library/Makefiles/Instance/application.make:145: internal-app-run-compile-submake] Error 2
gmake[3]: *** [/System/Library/Makefiles/Master/rules.make:297: Workspace.all.app.variables] Error 2
gmake[2]: *** [/System/Library/Makefiles/Master/application.make:38: internal-all] Error 2
make[1]: *** [/System/Library/Makefiles/Master/serial-subdirectories.make:53: internal-all] Error 2
make[1]: Leaving directory '/Local/Users/jmaloney/Documents/gershwin-build/repos/gershwin-workspace'
make: *** [Makefile:10: system] Error 1
jmaloney@pi ~/D/gershwin-build(main) % sudo ./bootstrap.sh
Detected OS: debian
Checking packages in: requirements/debian.txt
All required packages are already installed.
```

Start with Workspace/Network/NetworkVolumeManager.m around line 530 and inspect the build target and dependency handling for SFTPMount. Review bootstrap.sh and requirements/debian.txt, then reproduce the build on the reported Raspberry Pi OS environment. Done means Workspace links successfully without the undefined SFTPMount reference.

Written by the indexing model from the issue text.