ci: convert json-validation to typescript (@fehmer) (monkeytypegame#6899)

- convert json-validation to typescript
- integrate tests for assets back into the json-validation script

Author: fehmer

frontend/__tests__/constants/fonts.spec.ts

@@ -7,7 +7,7 @@
     "eslint": "eslint \"./**/*.ts\"",
     "oxlint": "oxlint .",
     "lint": "npm run oxlint && npm run eslint",
-    "validate-json": "node ./scripts/json-validation.cjs",
+    "validate-json": "tsx ./scripts/json-validation.ts",
     "audit": "vite-bundle-visualizer",
     "dep-graph": "madge -c -i \"dep-graph.png\" ./src/ts",
     "ts-check": "tsc --noEmit",
@@ -63,6 +63,7 @@
     "postcss": "8.4.31",
     "sass": "1.70.0",
     "subset-font": "2.3.0",
+    "tsx": "4.16.2",
     "typescript": "5.5.4",
     "unplugin-inject-preload": "3.0.0",
     "vite": "6.3.4",