CI build broke after adding `alembic/` and `db/` directories — flat-layout
auto-discovery saw three top-level dirs and refused to pick. Make it
explicit: only `app/` is a Python package, the rest are ops/migration data.
- backend/alembic/* — alembic infra (env.py, script.py.mako). versions/ empty
for now; first migration goes in Stage 2a when models are finalized.
- backend/Dockerfile: bake alembic.ini + alembic/ into the image so
`docker compose exec backend alembic upgrade head` works in prod.
- backend/db/init/99_drop_unused_extensions.sql + bind-mount in both compose
files: drops postgis-image's TIGER/topology/fuzzystrmatch on fresh volumes.
- .pre-commit-config.yaml + pre-commit in dev deps: ruff/prettier on commit
to stop CI failures like UP035 from leaking out.
- ops/backup.sh, ops/restore.sh: pg_dump cron script with optional Selectel S3
upload. 7-day local retention. Restore guard: requires RESTORE_CONFIRM=yes.
- Makefile: new targets `make migration NAME=...`, `make pre-commit-install`.
- backend/.env.example: SENTRY_DSN comment with sentry.io reference.
