ci(backend): type-check with ty and fix existing type errors

[klin2686]

Summary

1. Adds the ty type checker to the backend, enforced in CI and in the pre-commit hook.
2. Fixes the 99 type errors ty found, mostly by narrowing nullable values and correcting annotations.
3. Makes the 24 auto-set timestamp columns NOT NULL, since the response schemas already promise them as non-null.

What changed

Backend

Models and migrations

alembic upgrade head required — 1 revision.

• Makes every default=utcnow timestamp NOT NULL (created_at, updated_at, last_active_at, joined_at, submitted_at across 16 tables), filling any NULLs first. (63863039d4f1)
• Annotates those columns as Mapped[datetime]; .claude/rules/models-and-migrations.md now says auto-set timestamps aren't nullable.
• Declares TournamentRole.member_count = 0 as a plain class attribute (not a column), so the value with_member_counts() sets is typed.
• Types down_revision as str | Sequence[str] | None in alembic/script.py.mako and the two existing merge revisions, which have tuple parents.

Schemas and routes

• No endpoint or response shape changes.
• Swaps the unpack order in TournamentSummary(...) and AdminTournamentRead(...) (**counts first) to avoid a ty false positive; no runtime effect.
• Marks EventTrackDetailRead.needs narrowing list[EventStaffingNeed] to list[EventStaffingNeedRead] with # ty: ignore[invalid-attribute-override], an intended Pydantic subclass override.

Logic

• get_scoped_or_404 fetches with db.get(model, id_) instead of db.query(model).filter(model.id == id_).first(), so a row already in the session is reused.
• log_action and archive_tournament accept actor_id: int | None, which the nightly auto-archive passes for a tournament whose owner was deleted.
• apply_join_code_update, deactivate_join_code and is_join_code_expired take JoinCode; the JoinCodeLike Protocol lacked the label it writes.
• SessionLocal is always a sessionmaker (unbound without DATABASE_URL); get_db checks engine instead.
• resolve_person_refs and _resolve_chapter_creators return dict[int | None, PersonRefResponse], matching the None key they already add for deleted accounts.
• The onboarding add route reads the next order with func.max(TournamentForm.order); the reorder route sorts by the submitted orders.
• seed_members.py passes membership.user to write-through instead of a FakeUser stub.
• Narrows values that are never None in practice (form owner ids, email-change tokens, regex matches on reserved field keys) with asserts or explicit checks.

Tooling

• Adds ty as a dev dependency (locked at 0.0.86), configured in backend/ty.toml with error-on-warning = true.
• Excludes the three files of the deprecated Google Sheets import that fail type checking (routes/sheets.py, sheets_validation.py, sync_service.py); sync_sheet still writes membership columns dropped in 2df371e5.
• Adds a "Type check" step (uv run ty check) to the backend workflow.
• Renames that workflow from pytest.yml / "Backend Tests" to backend.yml / "Backend CI" (job test → checks), since it now lints and type-checks too.
• The workflow also runs when only its own file changes.
• Upgrades actions/checkout to v7 in backend.yml and release.yml, and actions/setup-node to v7 in release.yml, which run on Node 24 instead of the deprecated Node 20.
• .githooks/pre-commit type-checks a copy of the staged backend, so unstaged edits don't affect the result.

Editor

• Adds .vscode/settings.json, pointing the ty and Ruff extensions at backend/.venv, setting ty.configurationFile, reporting ty diagnostics for the whole workspace and making Ruff the Python formatter.
• Adds .vscode/extensions.json recommending both extensions; .gitignore now ignores .vscode/* except these two files.

Out of scope

• Fixing or removing the Google Sheets import; it stays deprecated and unchecked.

Test plan

• pytest passes locally
• Migration included for every model change
• Clicked through the UI change in a browser (no UI change)

Automated

• tests/core/test_form_branching.py uses string field ids, matching FormField.id.
• tests/test_migrations.py covers the new revision against the models.
• uv run ty check and Ruff pass across backend/.

Manual

• Upgraded and downgraded the dev database through 63863039d4f1, and ran alembic check.
• Pre-commit hook fails on a type error that's staged, and ignores one that's only in the working tree.
• With the repo root as the workspace, ty's language server reports nothing for the excluded sheets files.
• release.yml is untested with the new action versions; it first runs at the next manual release.

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Project	Deployment	Actions	Updated
nexus	Ready	Preview	Oct 13, 2026 10:52pm UTC

[railway-app]

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