feat(tests): FoodFiles v2 SQL diff validator

[stackbilt-admin]

Summary

Closes #1. Opens the generator-accuracy feedback loop by diffing `generateSQL()` output against actual migration files for each FoodFiles v2 contract.

What this adds

• `tests/foodfiles-sql-diff.test.ts` — vitest test that walks every `*.contract.ts` under `apps/api/src/contracts/`, dynamically imports it, runs `generateSQL()`, parses the result, and structurally diffs it against the CREATE TABLE from `apps/api/db/migrations/`.
• `vitest.config.ts` — adds `@stackbilt/contracts` → `src/index.ts` alias so FoodFiles contract files resolve their package import without a published build.

What the diff checks

Dimension	Covered
Column-name set parity	✅
SQLite type parity (TEXT/INTEGER/REAL/BLOB)	✅
NOT NULL parity	✅
DEFAULT presence parity	✅
Index shape	❌ (gate on #2/#3)
Foreign keys	❌ (generator v0.1 limit)
CHECK constraints	❌ (generator v0.1 limit)

Initial run results

7 contracts scanned, 6 real drifts caught on first execution — exactly the signal the issue asked for:

• `MealPlan`: `servings`, `created_at`, `updated_at` — contract requires NOT NULL but migration allows NULL
• `PantryItem`: `location`, `created_at`, `updated_at` — same NOT NULL mismatch

These are encoded in a `KNOWN_DRIFTS` allowlist so CI stays green today. Fixing a drift removes its entry → regressions re-fail the test.

CI behavior

Auto-skips when `FOODFILES_PATH` doesn't resolve to a directory containing `apps/api/src/contracts`. CI without FoodFiles checked out stays green; local runs opt in via env var.

Usage

```bash
FOODFILES_PATH=../foodfilesapi_v2 npx vitest run tests/foodfiles-sql-diff.test.ts
```

Test plan

• 7/7 tests pass locally against foodfilesapi_v2
• Suite auto-skips when FOODFILES_PATH missing
• Existing `routes.test.ts` (36 tests) still passes
• Follow-up: investigate whether NOT NULL drifts should be fixed in contracts or migrations

Closes #1

🤖 Generated with Claude Code