Rename peo4c to peo

Renames the Python package, environment variables (PEO4C_* to PEO_*), the
SQL helper schema, image paths and the entrypoint script.

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

docker/pgadmin/config_distro.py

@@ -1,6 +1,6 @@
 # SPDX-FileCopyrightText: 2026 Bart Broere
 # SPDX-License-Identifier: GPL-3.0-or-later
-# pgAdmin settings for the peo4c image, loaded via CONFIG_DISTRO_FILE_PATH.
+# pgAdmin settings for the peo image, loaded via CONFIG_DISTRO_FILE_PATH.
 # Paths derived from DATA_DIR in pgAdmin's config.py are computed before this
 # file is applied, so they are all set explicitly here.