feat: pictures table, Hetzner S3 upload/delete, auto-migration

- pictures table with UUID, status enum, timestamps, blurhash, design
- Auto-trigger updates updated_at on every row change
- POST /api/pictures/:id/upload  → upload file to Hetzner snakkimo bucket
- DELETE /api/pictures/:id       → removes DB row + Hetzner file
- PATCH /api/pictures/:id        → auto-sets published/blocked timestamps
- Migration runs on every server start (idempotent)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -8,11 +8,15 @@
     "dev": "nodemon src/index.js"
   },
   "dependencies": {
-    "express": "^4.19.2",
-    "pg": "^8.11.3",
-    "dotenv": "^16.4.5",
+    "@aws-sdk/client-s3": "^3.1050.0",
+    "@aws-sdk/lib-storage": "^3.1050.0",
     "cors": "^2.8.5",
-    "express-validator": "^7.1.0"
+    "dotenv": "^16.4.5",
+    "express": "^4.19.2",
+    "express-validator": "^7.1.0",
+    "multer": "^2.1.1",
+    "pg": "^8.11.3",
+    "uuid": "^14.0.0"
   },
   "devDependencies": {
     "nodemon": "^3.1.0"