chore: migrate to TypeScript

- Convert all .js files to .tsx/.ts
- Add types for data structures (MuseumRecord, Metrics, etc.)
- Add type declarations for react-chartjs-2
- Configure tsconfig with relaxed strictness for gradual adoption
- All components now use TypeScript

package.json

@@ -42,5 +42,12 @@
       "last 1 firefox version",
       "last 1 safari version"
     ]
+  },
+  "devDependencies": {
+    "@types/node": "^25.2.0",
+    "@types/react": "^19.2.10",
+    "@types/react-dom": "^19.2.3",
+    "@types/react-router-dom": "^5.3.3",
+    "typescript": "^5.9.3"
   }
 }