feat: scaffold klarbild foundation (astro+postgres+s3, auth, migrations, health)

- Astro 5 SSR (node standalone) + React, OKLCH tokens (no tailwind)
- migrations/001_init.sql: full schema per 03-datenmodell-api
- lib: db+migrations, crypto (AES-256-GCM), auth (argon2+signed session, ratelimit),
  storage (S3/MinIO, presigned URLs), openrouter (POST /v1/images, cost)
- middleware: init-once + session guard + admin gate; /api/health (db+storage)
- login + studio placeholder; seeds (till/lea, default recipes); Dockerfile
- verified: astro build passes

tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "astro/tsconfigs/strict",
+  "compilerOptions": {
+    "jsx": "react-jsx",
+    "baseUrl": ".",
+    "paths": { "@/*": ["src/*"] }
+  },
+  "include": ["src", "scripts"],
+  "exclude": ["dist", "node_modules"]
+}