Load .env in env.ts so SvelteKit SSR sees DATABASE_URL etc.

Without dotenv/config the SvelteKit dev server SSR sees only the
ambient shell env, so the Zod validator rejected all four required
variables with Required. drizzle.config.ts already does this; match.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/server/env.ts

@@ -1,3 +1,4 @@
+import 'dotenv/config';
 import { z } from 'zod';
 
 const EnvSchema = z.object({