Add VPS PostgreSQL backup/restore scripts and docs

[Spbd1]

Motivation

• Provide simple, safe VPS helpers to back up and restore the Docker Compose PostgreSQL database without exposing the DB port.
• Make it easy to create timestamped off-server backups before updates or migrations and to restore only after explicit confirmation.
• Keep local dump files out of the repository and document the recommended backup/restore workflow for VPS deployments.

Description

• Add scripts/backup-postgres.sh, a strict Bash helper (set -euo pipefail) that reads POSTGRES_USER and POSTGRES_DB from .env with safe defaults hcg / hidden_cost_game, creates backups/, and runs docker compose exec -T postgres pg_dump to write a timestamped .sql file and print the output path.
• Add scripts/restore-postgres.sh, which requires a backup file path argument, validates the file, prints a prominent warning, requires typing RESTORE to proceed, and streams the SQL into the DB with docker compose exec -T postgres psql (no DB port exposure).
• Update docs/VPS_DEPLOYMENT.md to recommend running ./scripts/backup-postgres.sh before updates, explain where backups are stored, show scp examples for copying backups off/on the VPS, and document the restore warning and usage of ./scripts/restore-postgres.sh.
• Add backups/ to .gitignore so repository-local dumps are not accidentally committed.

Testing

• Shell static check: bash -n scripts/backup-postgres.sh scripts/restore-postgres.sh was run (shellcheck not available) and returned no syntax errors.
• Typecheck: npm run typecheck completed successfully.
• Lint: npm run lint completed successfully with no ESLint warnings.
• Build: npm run build completed a successful Next.js production build and page generation.

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Codex Task