chore(deps): clear every npm audit and pip-audit finding

Frontend:
    - react-router/-dom 7.18.1 -> 7.18.2. The RSC-mode CSRF advisory was carried
      as a documented exception in the audit gate because its only fix was the
      8.3.0 major; upstream backported it, so the exemption lapsed on its own --
      an entry only holds while fixAvailable.isSemVerMajor is true. The allowlist
      is now empty; the machinery stays for the next one.
    - dompurify 3.4.12 -> 3.4.13. Ships in the app, but the path is unreachable:
      no hooks registered, IN_PLACE never used.
    - js-yaml override ^4.3.0 -> ^5.2.3 (fix not backported below 5.x, so a
      major) and nanoid override ^3.3.18. Both dev-only, via eslint and postcss.
      eslintrc calls only load(), on the legacy .eslintrc.yml path this repo does
      not use; eslint, vite build and 2861 frontend tests pass on it.

    Backend:
    - cryptography >=48.0.1 -> >=50.0.0, aiohttp >=3.14.0 -> >=3.14.3, pyopenssl
      >=26.3.0 -> >=26.4.0. CI resolves from scratch and was already installing
      the fixed releases; the floors cover the case CI does not, an existing venv
      where >= is satisfied and `pip install -r` upgrades nothing. pyOpenSSL has
      to move with cryptography -- each release caps it to a narrow window, so a
      stale pyOpenSSL pins cryptography below its own fix line.

frontend/package.json

@@ -40,7 +40,7 @@
     "react-dom": "^19.2.0",
     "react-i18next": "^16.3.5",
     "react-markdown": "^9.1.0",
-    "react-router-dom": "7.18.1",
+    "react-router-dom": "7.18.2",
     "react-simple-keyboard": "^3.8.164",
     "recharts": "^3.5.1",
     "remark-gfm": "^4.0.1",
@@ -48,9 +48,10 @@
   },
   "overrides": {
     "minimatch": "^10.2.1",
-    "brace-expansion": "^5.0.8",
-    "js-yaml": "^4.3.0",
-    "react-router": "7.18.1"
+    "brace-expansion": "^5.0.9",
+    "js-yaml": "^5.2.3",
+    "nanoid": "^3.3.18",
+    "react-router": "7.18.2"
   },
   "devDependencies": {
     "@eslint/js": "^9.39.1",