chore: full implementation of code review recommendations (security, quality, tests)

package.json

@@ -16,6 +16,7 @@
   },
   "dependencies": {
     "@types/leaflet": "^1.9.21",
+    "bcryptjs": "^3.0.3",
     "gray-matter": "^4.0.3",
     "js-yaml": "^4.1.1",
     "leaflet": "^1.9.4",
@@ -27,6 +28,7 @@
   },
   "devDependencies": {
     "@playwright/test": "^1.58.2",
+    "@types/bcryptjs": "^2.4.6",
     "@types/js-yaml": "^4.0.9",
     "@types/node": "^20",
     "@types/react": "^19",