test(integration): DB-backed harness validating shipped SQL (045/042/044/043)

Root-cause fix for 'correctness depended on post-deploy manual audits'.
Separate psql-driven suite (pnpm test:integration, own vitest config,
integration/ outside __tests__ so the hermetic pnpm test gate is
untouched; self-skips without a DB). 18 tests run against real Postgres:
- 045 class_signup_tx/class_cancel_tx: RETURNS TABLE->array shape the
  actions destructure, capacity/waitlist/dedupe, and the per-session
  advisory lock under TWO concurrent connections (D11 proven, never
  over-enrolls).
- 042 equipment exclusion constraint (overlap 23P01; cancelled/adjacent
  ok). 044 self-change trigger (role + payment cols blocked; service
  bypass). 043 members_update WITH CHECK (cross-space move blocked).
Disproves the pass-52 flagged risk (signup rpc-shape). Non-runtime;
default pnpm test still 532/26 hermetic; build clean.

package.json

@@ -9,6 +9,7 @@
     "lint": "eslint .",
     "test": "vitest",
     "test:ui": "vitest --ui",
+    "test:integration": "vitest run --config vitest.integration.config.ts",
     "test:e2e": "playwright test",
     "test:e2e:ui": "playwright test --ui"
   },