Add PostgreSQL with automated hot backup setup

Weekly full backups via pg_basebackup and continuous WAL archiving
for point-in-time recovery, running as Docker Compose services.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,50 @@
+
+services:
+  postgres-db:
+    image: postgres:18
+    container_name: postgres-db
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+      POSTGRES_DB: ${POSTGRES_DB}
+    ports:
+      - "${PGPORT}:5432"
+    volumes:
+      - postgres_data:/var/lib/postgresql
+      - /data/backup/postgres/wal:/backup/wal
+      - ./init-replication-hba.sh:/docker-entrypoint-initdb.d/init-replication-hba.sh:ro
+    command:
+      - postgres
+      - -c
+      - wal_level=replica
+      - -c
+      - archive_mode=on
+      - -c
+      - archive_command=test ! -f /backup/wal/%f && cp %p /backup/wal/%f
+
+  postgres-backup:
+    image: postgres:18
+    container_name: postgres-backup
+    restart: unless-stopped
+    depends_on:
+      - postgres-db
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER}
+      PGPASSWORD: ${POSTGRES_PASSWORD}
+    volumes:
+      - /data/backup/postgres:/backup
+    entrypoint: ["/bin/bash", "-c"]
+    command:
+      - |
+        mkdir -p /backup/wal /backup/full
+        while true; do
+          STAMP=$$(date +%Y-%m-%d_%H-%M-%S)
+          echo "Starting full backup: full_$$STAMP"
+          pg_basebackup -h postgres-db -U "$$POSTGRES_USER" -D "/backup/full/full_$$STAMP" -Fp -Xs -P
+          echo "Full backup complete: full_$$STAMP"
+          sleep 604800
+        done
+
+volumes:
+  postgres_data: