feat: build core API, fraud engine, notifier, and frontend

Phase 1 — Core API (Go):
- Events, guests, tokens, RSVPs CRUD on PostgreSQL via pgx/v5
- HMAC-signed per-guest tokens with format validation
- Health endpoint with DB ping, slog JSON logging, graceful shutdown

Phase 2 — NATS + Fraud Engine:
- NATS JetStream pub/sub with explicit-ack consumers
- Python/FastAPI fraud engine with heuristic risk scoring
  (fingerprint mismatch, IP change, missing signals, repeated access)
- gRPC sync scoring with 250ms fail-open timeout
- Per-guest baseline tracking; risk bands low/medium/high/block

Phase 3 — Notifications + Frontend:
- Notification worker scaffolding (Twilio/SES stubs, retry/backoff)
- Nuxt 3 frontend with Tailwind dark theme + brand green
- Live monitor via WebSocket with auto-reconnect
- Activity history endpoint backfills monitor with RSVPs +
  scored access checks (including blocked attempts)

UX polish:
- Marketing-friendly landing page (hero mockup, how-it-works,
  features, use cases, testimonials, FAQ, final CTA)
- Animated layered card mockups on landing + new-event page
- Plus-ones stepper, RSVP status badges, filter buttons
- Friendly access-check labels (Verified/Review/Suspicious/Blocked)
- Dashboard hydration fix via ClientOnly wrapper

Infrastructure:
- docker-compose for full local dev (postgres, nats, api,
  fraud-engine, notifier, frontend)
- Multi-stage Dockerfiles, non-root UID 1000
- Integration tests with testcontainers-go

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/composables/useHost.ts

@@ -0,0 +1,43 @@
+// Demo-grade host bootstrap. Real auth would replace this entirely; for now
+// we upsert by email and stash the host id in localStorage.
+interface User {
+  id: string
+  email: string
+  name: string
+}
+
+const STORAGE_KEY = 'gg.host'
+
+export function useHost() {
+  const host = useState<User | null>('gg-host', () => null)
+
+  if (import.meta.client && !host.value) {
+    const raw = window.localStorage.getItem(STORAGE_KEY)
+    if (raw) {
+      try {
+        host.value = JSON.parse(raw)
+      } catch {
+        window.localStorage.removeItem(STORAGE_KEY)
+      }
+    }
+  }
+
+  async function bootstrap(email: string, name: string) {
+    const u = await useApi<User>('/users', {
+      method: 'POST',
+      body: { email, name },
+    })
+    host.value = u
+    if (import.meta.client) {
+      window.localStorage.setItem(STORAGE_KEY, JSON.stringify(u))
+    }
+    return u
+  }
+
+  function clear() {
+    host.value = null
+    if (import.meta.client) window.localStorage.removeItem(STORAGE_KEY)
+  }
+
+  return { host, bootstrap, clear }
+}