feat(deploy): nightly database backups with verified restore (M7)

A backup container dumps the database every night, keeps 14 daily and 8 weekly
copies and once a week restores a copy into a scratch database to check tables
and row counts. update.sh takes a copy before updating, restore.sh brings one
back and keeps the old database aside. CI runs the dump, verify and restore
cycle on the database the end-to-end journey filled.

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

.gitea/workflows/ci-db.yml

@@ -9,11 +9,13 @@ on:
     paths:
       - 'services/api/**'
       - 'services/recommender/**'
+      - 'deploy/backup.sh'
       - '.gitea/workflows/ci-db.yml'
   pull_request:
     paths:
       - 'services/api/**'
       - 'services/recommender/**'
+      - 'deploy/backup.sh'
       - '.gitea/workflows/ci-db.yml'
 
 concurrency:
@@ -64,3 +66,26 @@ jobs:
         run: |
           uv sync --frozen
           uv run pytest -q tests/test_db_integration.py
+      # База уже наполнена сценариями выше — проверяем настоящий цикл копия → проверка → восстановление.
+      - name: Бэкап, проверка и восстановление (deploy/backup.sh)
+        env:
+          PGHOST: postgres
+          PGUSER: pipu
+          PGPASSWORD: pipu
+          PGDATABASE: pipu
+          BACKUP_DIR: /tmp/backups
+          VERIFY_EXACT: "1"
+        run: |
+          SUDO=$(command -v sudo || true)
+          $SUDO install -d /usr/share/postgresql-common/pgdg
+          $SUDO curl -fsSLo /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc https://www.postgresql.org/media/keys/ACCC4CF8.asc
+          echo "deb [signed-by=/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc] https://apt.postgresql.org/pub/repos/apt $(. /etc/os-release && echo "$VERSION_CODENAME")-pgdg main"             | $SUDO tee /etc/apt/sources.list.d/pgdg.list >/dev/null
+          $SUDO apt-get update -qq && $SUDO apt-get install -y -qq postgresql-client-17 >/dev/null
+          export PATH=/usr/lib/postgresql/17/bin:$PATH
+          before=$(psql -Atc "SELECT count(*) FROM tracks")
+          file=$(bash deploy/backup.sh once)
+          bash deploy/backup.sh verify "$file"
+          bash deploy/backup.sh restore "$file"
+          after=$(psql -Atc "SELECT count(*) FROM tracks")
+          echo "tracks: $before → $after"
+          test "$before" = "$after"