Stage 2 partial: migrations + middleware + authz + API contracts

What ships (verifiable without live DB, 64 new tests):
- db/migrations/0000_initial_schema.sql (Drizzle-generated, 7 tables) + .down.sql + registry entry
- db/migrations/rehearse.ts: forward-then-rollback round-trip with row-count hash check (DoD 2.2)
- infra/docker-compose.yml: postgres 17 + redis 7 + openobserve for local dev (5433/6380/5080)
- packages/schema/src/rate-limit.ts: pluggable store; 4 tests including 21st-of-20 reject (DoD 2.4)
- packages/schema/src/csrf.ts: HMAC double-submit token; 8 tests covering forgery + tamper + malformed
- packages/schema/src/authz.ts: 3-role Cerbos-equivalent rules (operator/approver/viewer); 6 tests
- packages/schema/src/api-contracts.ts: Zod schemas for /api/content, /api/approvals, /api/publications, /api/feature-flags + idempotencyKeyOf; 11 tests

What defers to live-DB session:
- 2.3 admin route handlers integration tests (401/403/200/422 contract suite)
- 2.2 actual rehearsal execution against staging DB

Total: 79/79 tests pass across 9 files in 4 packages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

db/migrations/README.md

@@ -21,7 +21,7 @@
 
 | # | Date | Name | Plan | Forward cost | Rollback cost | Notes |
 |---|---|---|---|---|---|---|
-| — | — | — | — | — | — | No migrations yet — first migration lands in Stage 2.1 |
+| 0000 | 2026-04-26 | initial_schema | Phase 1 Stage 2.1 | Low (empty DB; CREATE TABLE only) | Low (DROP TABLE on 7 tables, no data loss possible on empty DB) | Establishes 7 tables: content, publications, approvals, metrics, linkedin_tokens, audit, outlet_feature_flags. Generated from `packages/schema/src/db.ts` via drizzle-kit. |
 
 ## Rehearsal