Persist zoxide directory history across container recreations

Zoxide stores its database at ~/.local/share/zoxide/db.zo. Without a
named volume, the 'z <fragment>' jump targets are lost on every
'docker compose up --force-recreate'.

Add devbox-zoxide named volume in docker-compose.yml and
docker-compose.shared.yml, add ~/.local/share/zoxide to the
entrypoint ownership-fix loop per AGENTS.md convention, and update
the data-persistence tables in README.md and DOCKER_HUB.md.

docker-compose.shared.yml

@@ -52,6 +52,9 @@ services:
       # Persist bash history across container recreations
       - devbox-shell-history:/home/developer/.cache/bash
 
+      # Persist zoxide directory history ('z <fragment>' to jump)
+      - devbox-zoxide:/home/developer/.local/share/zoxide
+
       # Persist uv data (Python installs)
       - devbox-uv:/home/developer/.local/share/uv
 
@@ -61,4 +64,5 @@ services:
 volumes:
   devbox-data:
   devbox-shell-history:
+  devbox-zoxide:
   devbox-uv: