The llamalink service fails to start because ProtectSystem=strict only
allows writes to ReadWritePaths=/opt/llamalink/data, but the default
DATABASE_URL=sqlite:///./llamalink.db resolves relative to WorkingDirectory.
With WorkingDirectory=/opt/llamalink, the db lands at /opt/llamalink/llamalink.db
which is not in ReadWritePaths, causing sqlite open to fail.
Setting WorkingDirectory=/opt/llamalink/data aligns with the package layout
(postinst creates /opt/llamalink/data) and makes the default ./llamalink.db
resolve to the correct writable location.