feat(backend): Dokumente und Bilder mit lokalem Datei-Upload (Modul 29)

DocumentsModule (Document: entityType/entityId, Dateiname, MIME-Typ,
Groesse, Speicherpfad, Hochgeladen-von) fuer Bienenstand/Volk/Koenigin/
Durchsicht/Honigcharge. Upload als multipart/form-data (Multer, 10 MB
Limit, MIME-Allowlist jpeg/png/webp/pdf), Speicherung unter
DOCUMENTS_STORAGE_PATH (austauschbar). ARCHITECTURE.md Annahme 7
dokumentiert die Multi-Replica-Einschraenkung ohne geteiltes Volume.

ApiCore-Backend/package-lock.json

@@ -40,6 +40,7 @@
         "@types/cookie-parser": "^1.4.10",
         "@types/express": "^5.0.0",
         "@types/jest": "^30.0.0",
+        "@types/multer": "^2.2.0",
         "@types/node": "^24.0.0",
         "@types/passport-jwt": "^4.0.1",
         "@types/pdfkit": "^0.17.6",
@@ -3543,6 +3544,16 @@
       "integrity": "sha512-GsCCIZDE/p3i96vtEqx+7dBUGXrc7zeSK3wwPHIaRThS+9OhWIXRqzs4d6k1SVU8g91DrNRWxWUGhp5KXQb2VA==",
       "license": "MIT"
     },
+    "node_modules/@types/multer": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@types/multer/-/multer-2.2.0.tgz",
+      "integrity": "sha512-3U1troeqGV8Ntp7Q3klwf4zr23VEoqYVocYXaswm9+8z3O9UHDYAqLxjJ/h550iRADTjKdOdhhasXw6gD6kYtg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/express": "*"
+      }
+    },
     "node_modules/@types/node": {
       "version": "24.13.3",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-24.13.3.tgz",