Security hardening: auth encapsulation, pool restriction, rate limiting, invites, async webhooks

Phase 1 (Security Critical):
- Auth plugin encapsulation: replaced global addHook with Fastify plugin scope
- Removed startsWith URL matching; public routes registered outside auth scope
- JWT verify now enforces algorithms: ['HS256'] (prevents algorithm confusion)
- Raw pool no longer exported from db.ts; systemQuery() + getPoolForAuth() instead
- withTenant() remains primary tenant-scoped query path

Phase 2 (Infrastructure):
- docker-compose.yml: all secrets via env var substitution (${VAR:-default})
- Per-service Postgres users (dd0c_drift, dd0c_alert, etc.) in docker-init-db.sh
- .env.example with all configurable secrets
- build-push.sh uses $REGISTRY_PASSWORD instead of hardcoded
- .gitignore excludes .env files
- @fastify/rate-limit: 100 req/min global, 5/min login, 3/min signup
- CORS_ORIGIN default changed from '*' to 'http://localhost:5173'

Phase 3 (Product):
- Team invite flow: tenant_invites table, POST /invite, GET /invites, DELETE /invites/:id
- Signup accepts optional invite_token to join existing tenant
- Async webhook ingestion (P3): LPUSH to Redis, BRPOP worker, dead-letter queue

Console:
- All 5 product modules wired: drift, alert, portal, cost, run
- PageHeader accepts children prop
- 71 modules, 70KB gzipped production build

All 6 projects compile clean (tsc --noEmit).

products/05-aws-cost-anomaly/migrations/003_invites.sql

@@ -0,0 +1,13 @@
+CREATE TABLE IF NOT EXISTS tenant_invites (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  tenant_id UUID NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
+  email TEXT NOT NULL,
+  role TEXT NOT NULL DEFAULT 'member' CHECK (role IN ('admin', 'member', 'viewer')),
+  token TEXT NOT NULL UNIQUE,
+  invited_by UUID NOT NULL REFERENCES users(id),
+  expires_at TIMESTAMPTZ NOT NULL DEFAULT NOW() + INTERVAL '7 days',
+  accepted_at TIMESTAMPTZ,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_tenant_invites_token ON tenant_invites(token);
+CREATE INDEX IF NOT EXISTS idx_tenant_invites_email ON tenant_invites(email);