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>

fraud-engine/app/config.py

@@ -0,0 +1,28 @@
+from pydantic import Field
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_prefix="GG_", env_file=".env", extra="ignore")
+
+    env: str = Field(default="development")
+    http_addr: str = Field(default="0.0.0.0:8081")
+    grpc_addr: str = Field(default="0.0.0.0:9091")
+    nats_url: str = Field(default="nats://localhost:4222")
+    stream_name: str = Field(default="GUESTGUARD")
+    consumer_durable: str = Field(default="fraud-engine-access")
+
+    @property
+    def host(self) -> str:
+        return self.http_addr.split(":", 1)[0] or "0.0.0.0"
+
+    @property
+    def port(self) -> int:
+        parts = self.http_addr.rsplit(":", 1)
+        if len(parts) == 2 and parts[1].isdigit():
+            return int(parts[1])
+        return 8081
+
+
+def load_settings() -> Settings:
+    return Settings()