Devcontainer: enable bash-completion and set UTF-8 locale

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.devcontainer/Dockerfile

@@ -7,17 +7,21 @@ ARG USER_GID=$USER_UID
 
 # git + openssh-client: git over the host's forwarded SSH agent
 # gcc, libc-dev, libpq-dev: build psycopg2 from requirements.txt
-# postgresql-client, wait-for-it: scripts/db-setup.sh, scripts/psql.sh
+# postgresql-client, wait-for-it: database scripts
 # curl, ca-certificates: Claude Code installer
-# vim: personal preferences
+# vim, bash-completion: personal preferences
 RUN apt-get -y update && \
     apt-get install --no-install-recommends -y \
         git openssh-client make curl ca-certificates sudo \
         gcc libc-dev libpq-dev \
         postgresql-client wait-for-it \
-        vim && \
+        vim bash-completion && \
     apt-get clean && rm -rf /var/lib/apt/lists/*
 
+# Load bash-completion in every interactive shell (e.g. `make <TAB>`). Not in
+# ~/.bashrc, since the home dir is a volume (see devcontainer.json).
+RUN echo '. /usr/share/bash-completion/bash_completion' >> /etc/bash.bashrc
+
 RUN groupadd --gid $USER_GID $USERNAME && \
     useradd --uid $USER_UID --gid $USER_GID -m -s /bin/bash $USERNAME && \
     echo "$USERNAME ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/$USERNAME && \