feat(realtime): Fase 2b.0 infra + first R-series tests green

Enable postgres_changes broadcasts on shopping_items / shopping_lists and prove
the path end-to-end with Vitest Realtime tests and a pgTAP configuration check.

Infra changes that were silently blocking events
- Migration 007: shopping_items + shopping_lists added to supabase_realtime
  publication with REPLICA IDENTITY FULL (UPDATE/DELETE payloads need the full
  row so list_id-based filters work and RLS can evaluate DELETE against OLD)
- Realtime service: DB_USER=supabase_admin (superuser; supabase_replication_admin
  lacks CREATE on the `realtime` schema that the service auto-creates per tenant)
- Realtime service: SELF_HOST_TENANT_NAME=realtime so the seed tenant name
  matches the default supabase-js resolves for localhost URLs (was realtime-dev
  → TenantNotFound)

Tests
- pgTAP 004_realtime_publication.sql — P-01..P-04: publication membership and
  REPLICA IDENTITY FULL for both shopping tables
- Vitest realtime-postgres-changes.test.ts — R-01 INSERT broadcast,
  R-02 UPDATE carries full row, R-03 list_id filter isolates events
- test-utils realtime-helpers.ts — subscribePostgresChanges() returns a
  waitFor(predicate, timeout) helper that captures the SUBSCRIBED handshake
  before returning so mutations issued right after are not lost
- createClientAs now calls realtime.setAuth(token) so the server evaluates
  RLS against the test user's JWT
- Justfile test-db now globs supabase/tests/*.sql so new pgTAP files are picked
  up automatically

Totals: 54→57 Vitest, 12→16 pgTAP, 15 Playwright = 88 tests green.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

CLAUDE.md

@@ -8,7 +8,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Status
 
-**Fase 0 complete. Fase 1 complete. Fase 2a complete. Full test suite green (54 Vitest + 12 pgTAP + 15 Playwright = 81 tests). ✅**
+**Fase 0 complete. Fase 1 complete. Fase 2a complete. Fase 2b — Realtime infra prep done and R-series tests green. Full test suite green (57 Vitest + 16 pgTAP + 15 Playwright = 88 tests). ✅**
 
 - `README.md` — full development plan, confirmed tech stack, Justfile reference, and technical warnings
 - `analysis/analisis-funcional.md` — complete functional specification (domain model, use cases, data models, business rules)