A PostgreSQL cluster/database freezes its encoding at initdb / CREATE
DATABASE time; a C (non-UTF-8) locale yields a SQL_ASCII cluster, which
makes psycopg3 return bytes and crashes SQLAlchemy. Harden the installer
and add a reusable pattern for future DB installers:
- ensure_utf8_locale_active: generate AND activate en_US.UTF-8 for the
install process before the server package runs initdb; abort if the
locale is not actually available
- create the database explicitly with TEMPLATE template0 ENCODING 'UTF8'
LC_COLLATE/LC_CTYPE 'en_US.UTF-8' instead of inheriting the cluster
default
- assert_db_encoding_utf8: post-install guard, abort with an actionable
message if pg_encoding_to_char is not UTF8 (catches old SQL_ASCII DBs
on re-run too)
- credentials/README docs use su - postgres -c (minimal LXCs have no sudo)
