fix(messages): reject non-decimal pagination values

[aiirvizionz]

Summary

• make chat message pagination accept only plain decimal integer query values
• reject surprising numeric spellings such as limit=1e2 and offset=0x10 instead of letting Number() coerce them into database ranges
• keep existing defaults, lower bounds, and max-limit capping behavior

Verification

• Direct Node check of normalizeMessagePagination for default, valid, malformed, non-decimal, and oversized limit cases

Note

pnpm vitest run src/app/api/chat/messages/pagination.test.js could not start in this Windows environment because project dependency setup runs a Unix-only postinstall (command, true) and the local Vitest config then fails while loading @vitejs/plugin-react/vite. The focused normalization behavior was verified directly with Node.