build(deps): add fast-check and Stryker as development dependencies

fast-check 4.10.2 for property tests; @stryker-mutator/core and the Vitest
runner 10.0.0 for mutation testing of the core libraries. Exact versions,
each published more than two weeks ago; the audit reports nothing new.

package.json

@@ -108,6 +108,8 @@
     "@axe-core/playwright": "^4.13.0",
     "@next/bundle-analyzer": "^16.3.8",
     "@playwright/test": "^1.64.0",
+    "@stryker-mutator/core": "10.0.0",
+    "@stryker-mutator/vitest-runner": "10.0.0",
     "@tailwindcss/postcss": "^4",
     "@tesseract.js-data/deu": "1.0.0",
     "@tesseract.js-data/eng": "1.0.0",
@@ -122,6 +124,7 @@
     "ajv": "^8.20.0",
     "eslint": "^9",
     "eslint-config-next": "16.3.8",
+    "fast-check": "4.10.2",
     "knip": "^6.41.0",
     "lefthook": "^2.2.2",
     "pdf-parse": "^2.4.5",