Bankkarte: IBAN pruefen + BIC/Bank offline aus Bundesbank-BLZ ausfuellen

Neuer Button "BIC & Bank aus IBAN abrufen" im Bankkarten-Modal fuellt BIC +
Banknamen automatisch und validiert dabei die IBAN-Pruefziffer (mod-97).
Leeres IBAN-Feld -> OK-Messagebox statt Anfrage.

Datenschutzfreundlich/offline: kein Dritt-Dienst. Nachschlag im eigenen
Backend ueber die Bundesbank-Bankleitzahlendatei (bankdata-germany) +
ibantools fuer die Pruefziffer. Die IBAN verlaesst nie den Server; zurueck
kommen nur oeffentliche Bankverzeichnis-Daten.

Endpoint: POST /api/bank-cards/iban-lookup (nur eingeloggt).
Wartung: bankdata-germany/ibantools ~quartalsweise per npm update ziehen.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/package-lock.json

@@ -12,6 +12,7 @@
         "@types/cookie-parser": "^1.4.10",
         "adm-zip": "^0.5.16",
         "archiver": "^7.0.1",
+        "bankdata-germany": "^2.2602.0",
         "bcryptjs": "^2.4.3",
         "cookie-parser": "^1.4.7",
         "cors": "^2.8.5",
@@ -21,6 +22,7 @@
         "express-rate-limit": "^8.4.0",
         "express-validator": "^7.2.0",
         "helmet": "^8.1.0",
+        "ibantools": "^4.5.4",
         "imapflow": "^1.2.8",
         "jsonwebtoken": "^9.0.2",
         "mailparser": "^3.9.3",
@@ -984,6 +986,15 @@
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     },
+    "node_modules/bankdata-germany": {
+      "version": "2.2602.0",
+      "resolved": "https://registry.npmjs.org/bankdata-germany/-/bankdata-germany-2.2602.0.tgz",
+      "integrity": "sha512-3iBD/cIKHZsmAaQIYEMsORhvMjILDTJ4gDQJYNVm+YXCzA5U96mUoB7KBy01rtwpFt/rKrNuCVNc8KZVx+jwpQ==",
+      "license": "MIT OR MPL-2.0",
+      "engines": {
+        "node": ">=20"
+      }
+    },
     "node_modules/bare-events": {
       "version": "2.8.2",
       "resolved": "https://registry.npmjs.org/bare-events/-/bare-events-2.8.2.tgz",
@@ -1992,6 +2003,12 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/ibantools": {
+      "version": "4.5.4",
+      "resolved": "https://registry.npmjs.org/ibantools/-/ibantools-4.5.4.tgz",
+      "integrity": "sha512-6jX1gh4aH6XH+o0ey+wtkMTzkcvsEta7DakIOZSng9voZYpMw3U+gK1+tZChk3aRcPcloEt0NOzksjaRZiqXbw==",
+      "license": "MIT or MPL-2.0"
+    },
     "node_modules/iconv-lite": {
       "version": "0.4.24",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.4.24.tgz",