feat(gateway): tier-detector with fail-fast PG/Valkey/pgvector probes (FED-M1-04) (#473)

apps/gateway/src/main.ts

@@ -20,10 +20,12 @@ import { Logger, ValidationPipe } from '@nestjs/common';
 import { FastifyAdapter, type NestFastifyApplication } from '@nestjs/platform-fastify';
 import helmet from '@fastify/helmet';
 import { listSsoStartupWarnings } from '@mosaicstack/auth';
+import { loadConfig } from '@mosaicstack/config';
 import { AppModule } from './app.module.js';
 import { mountAuthHandler } from './auth/auth.controller.js';
 import { mountMcpHandler } from './mcp/mcp.controller.js';
 import { McpService } from './mcp/mcp.service.js';
+import { detectAndAssertTier, TierDetectionError } from './bootstrap/tier-detector.js';
 
 async function bootstrap(): Promise<void> {
   const logger = new Logger('Bootstrap');
@@ -32,6 +34,20 @@ async function bootstrap(): Promise<void> {
     throw new Error('BETTER_AUTH_SECRET is required');
   }
 
+  // Pre-flight: assert all external services required by the configured tier
+  // are reachable. Runs before NestFactory.create() so failures are visible
+  // immediately with actionable remediation hints.
+  const mosaicConfig = loadConfig();
+  try {
+    await detectAndAssertTier(mosaicConfig);
+  } catch (err) {
+    if (err instanceof TierDetectionError) {
+      logger.error(`Tier detection failed: ${err.message}`);
+      logger.error(`Remediation: ${err.remediation}`);
+    }
+    throw err;
+  }
+
   for (const warning of listSsoStartupWarnings()) {
     logger.warn(warning);
   }