chore: remove unused 3P dependencies (zod, gray-matter, bcryptjs) and switch to native implementations

package.json

@@ -16,19 +16,15 @@
   },
   "dependencies": {
     "@types/leaflet": "^1.9.21",
-    "bcryptjs": "^3.0.3",
-    "gray-matter": "^4.0.3",
     "js-yaml": "^4.1.1",
     "leaflet": "^1.9.4",
     "next": "16.1.6",
     "react": "19.2.3",
     "react-dom": "19.2.3",
-    "thumbhash": "^0.1.1",
-    "zod": "^4.3.6"
+    "thumbhash": "^0.1.1"
   },
   "devDependencies": {
     "@playwright/test": "^1.58.2",
-    "@types/bcryptjs": "^2.4.6",
     "@types/js-yaml": "^4.0.9",
     "@types/node": "^20",
     "@types/react": "^19",
@@ -42,4 +38,4 @@
     "typescript": "^5",
     "vitest": "^4.0.18"
   }
-}
+}