Upgrade TypeScript to 6.0.3 across the entire monorepo

Replaces the i18next peer dep override workaround with a proper single
TypeScript version in the workspace catalog. All 15 packages typecheck
cleanly with TypeScript 6.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -35,9 +35,7 @@
       "path-to-regexp@<0.1.13": "0.1.13",
       "lodash@<4.18.1": "4.18.1",
       "react": "catalog:",
-      "react-dom": "catalog:",
-      "i18next>typescript": "5.9.3",
-      "react-i18next>typescript": "5.9.3"
+      "react-dom": "catalog:"
     },
     "onlyBuiltDependencies": [
       "@sentry/cli",

pnpm-workspace.yaml

@@ -21,5 +21,5 @@ catalog:
   react-dom: ^19.2.6
   react-router: ^7.15.1
   tailwindcss: ^4.3.0
-  typescript: ^5.8.3
+  typescript: ~6.0.3
   vite: ^8.0.13