Persist bash history and bake shell quality-of-life defaults

Two changes that address a longstanding frustration: bash history is
lost on every container recreate, and the container's ~/.bashrc and
~/.inputrc are stock Debian (no history tuning, no prefix search on
arrow keys, no integrations).

Added a named volume 'devbox-shell-history' mounted at ~/.cache/bash
with HISTFILE pointing there; history now survives 'docker compose up
--force-recreate'. The volume is added to both docker-compose.yml and
docker-compose.shared.yml, and ~/.cache/bash is registered in the
entrypoint ownership-fix loop per the AGENTS.md convention.

Baked rootfs/home/developer/.bash_aliases (sourced automatically by
Debian's default ~/.bashrc) and rootfs/home/developer/.inputrc into
the image. They give new containers: 100k-entry timestamped dedup
history with per-prompt flush, Up/Down arrow prefix history search,
case-insensitive coloured completion, aliases that prefer eza and
bat when present, git shortcuts, interactive rm/mv/cp, zoxide and
fzf (via 'fzf --bash') integration, and a [devbox] prompt marker.
The fzf integration uses 'fzf --bash' because we install fzf from
GitHub releases, not apt — the apt-path key-bindings aren't present.

Users who prefer their host's own shell config can uncomment two
commented bind-mount lines in docker-compose.yml to shadow the
baked defaults.

docker-compose.shared.yml

@@ -39,6 +39,9 @@ services:
       # Persist opencode data (auth, memory, session history)
       - devbox-data:/home/developer/.local/share/opencode
 
+      # Persist bash history across container recreations
+      - devbox-shell-history:/home/developer/.cache/bash
+
       # Persist uv data (Python installs)
       - devbox-uv:/home/developer/.local/share/uv
 
@@ -47,4 +50,5 @@ services:
 
 volumes:
   devbox-data:
+  devbox-shell-history:
   devbox-uv: