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.

entrypoint.sh

@@ -66,6 +66,7 @@ for parent in \
   /home/"$USER_NAME"/.local \
   /home/"$USER_NAME"/.local/share \
   /home/"$USER_NAME"/.local/state \
+  /home/"$USER_NAME"/.cache \
   /home/"$USER_NAME"/.config; do
   if [ -d "$parent" ] && [ "$(stat -c '%u' "$parent" 2>/dev/null)" != "$FINAL_UID" ]; then
     chown "$FINAL_UID":"$FINAL_GID" "$parent" 2>/dev/null || true
@@ -76,6 +77,7 @@ for dir in \
   /home/"$USER_NAME"/.local/share/opencode \
   /home/"$USER_NAME"/.local/state/opencode \
   /home/"$USER_NAME"/.local/share/uv \
+  /home/"$USER_NAME"/.cache/bash \
   /home/"$USER_NAME"/.rustup \
   /home/"$USER_NAME"/.cargo \
   /home/"$USER_NAME"/.vscode-server \