fix(backup): reimport postgres dump on restore (restore was a no-op)

The db service dumped the DB on backup (pg_dump pre-hook) but shipped no
restore hook, and a file-level restore does not reload into the running
postgres, so a restored backup silently kept the live (un-restored) state.
Add pg_backup.sh (backup=pg_dump|gzip into the postgresql_data volume;
restore=terminate conns + DROP DATABASE WITH FORCE + createdb + reimport),
mount it via a config, and wire the backupbot backup/restore hooks. Same
fix as the immich / mattermost-lts / ghost recipes.

compose.yml

@@ -49,7 +49,7 @@ services:
       interval: 30s
       timeout: 10s
       retries: 6
-      start_period: 5m
+      start_period: ${APP_START_PERIOD:-5m}
 
   db:
     image: postgres:13
@@ -63,6 +63,9 @@ services:
       - source: db_entrypoint
         target: /docker-entrypoint.sh
         mode: 0555
+      - source: pg_backup
+        target: /pg_backup.sh
+        mode: 0555
     entrypoint: /docker-entrypoint.sh
     environment:
       - POSTGRES_HOST_AUTH_METHOD=trust
@@ -72,9 +75,9 @@ services:
     deploy:
       labels:
         backupbot.backup: "true"
-        backupbot.backup.pre-hook: "bash -c 'PGPASSWORD=$$(cat $${POSTGRES_PASSWORD_FILE}) pg_dump -U $${POSTGRES_USER} $${POSTGRES_DB} > /tmp/backup.sql'"
-        backupbot.backup.post-hook: "rm -rf /tmp/backup.sql"
-        backupbot.backup.path: "/tmp/backup.sql"
+        backupbot.backup.pre-hook: "/pg_backup.sh backup"
+        backupbot.backup.volumes.postgresql_data.path: "backup.sql"
+        backupbot.restore.post-hook: "/pg_backup.sh restore"
 
   redis:
     image: redis:7.4-alpine
@@ -132,3 +135,6 @@ configs:
     name: ${STACK_NAME}_db_entrypoint_${DB_ENTRYPOINT_VERSION}
     file: entrypoint.postgres.sh.tmpl
     template_driver: golang
+  pg_backup:
+    name: ${STACK_NAME}_pg_backup_${PG_BACKUP_VERSION}
+    file: pg_backup.sh