feat: GPS-Track auf OpenSeaMap-Karte mit Leaflet visualisieren.

Leaflet wieder eingebunden, CSS über Vite gebündelt und doppelte Karten-Initialisierung behoben.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/package.json

@@ -17,6 +17,7 @@
     "i18next": "^26.3.0",
     "i18next-browser-languagedetector": "^8.2.1",
     "jspdf": "^4.2.1",
+    "leaflet": "^1.9.4",
     "lucide-react": "^1.16.0",
     "react": "^19.2.6",
     "react-dom": "^19.2.6",
@@ -24,6 +25,7 @@
   },
   "devDependencies": {
     "@eslint/js": "^10.0.1",
+    "@types/leaflet": "^1.9.21",
     "@types/node": "^24.12.3",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",