fix(deps): High-/Critical-Advisories schliessen, typecheck-Script

pnpm audit --prod meldete 1 critical und 8 high:
- next 16.3.5 -> 16.3.8 (critical), eslint-config-next mitgezogen
- nodemailer 9 -> 10.1.0 (Bruch nur: Node >= 20; Image laeuft auf Node 22)
- sharp >= 0.35.5 und source-map-js >= 1.2.2 per Override (transitiv ueber next)
- mariadb >= 3.5.4 (direkt und per Override)

Neues Script "typecheck" (Prisma-Clients erzeugen, tsc --noEmit) fuer das CI-Gate.
Lokal geprueft: lint, typecheck, 674 Tests, next build gruen; audit ohne high.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

package.json

@@ -7,6 +7,7 @@
     "build": "node scripts/generate-prisma-clients.mjs && next build",
     "start": "node scripts/generate-prisma-clients.mjs && next start",
     "lint": "eslint",
+    "typecheck": "node scripts/generate-prisma-clients.mjs && tsc --noEmit",
     "postinstall": "node scripts/generate-prisma-clients.mjs",
     "db:push": "node scripts/prisma-provider.mjs && prisma db push",
     "db:migrate": "node scripts/prisma-provider.mjs && prisma migrate dev",
@@ -31,17 +32,17 @@
     "bcryptjs": "^3.0.3",
     "ffmpeg-static": "^5.3.0",
     "jose": "^6.2.8",
-    "mariadb": "^3.5.3",
+    "mariadb": "^3.5.4",
     "motion": "^13.0.0",
-    "next": "16.3.5",
-    "nodemailer": "^9.1.1",
+    "next": "16.3.8",
+    "nodemailer": "^10.0.10",
     "otpauth": "^9.5.1",
     "pdfkit": "^0.19.1",
     "prisma": "^7.10.0",
     "qrcode": "^1.5.4",
     "react": "19.2.8",
     "react-dom": "19.2.8",
-    "sharp": "^0.35.4",
+    "sharp": "^0.35.5",
     "stripe": "^22.4.0",
     "zod": "^4.4.3",
     "zustand": "^5.0.14"
@@ -62,7 +63,7 @@
     "@vitejs/plugin-react": "^6.0.5",
     "dotenv": "^17.4.2",
     "eslint": "^9",
-    "eslint-config-next": "16.3.5",
+    "eslint-config-next": "16.3.8",
     "jsdom": "^30.0.1",
     "tailwindcss": "^4",
     "tsx": "^4",