[Bug] maxSizeMB prop silently accepted as NaN / 0 / negative

I will pay for a fixed file - details below. ## Bug In [`components/FileUpload.tsx`](https://github.com/Hazyshades/Sendly-Test-Repo/blob/main/components/FileUpload.tsx) `maxSizeMB = 5` is trusted blindly. `maxSizeMB={NaN}` makes every comparison false (all files pass); `{0}` or negative rejects everything with nonsense copy like `exceeds 0MB limit`. Add a dev-time guard: validate/coerce the prop, fall back to default with a `console.warn` in development builds. ## Acceptance criteria - [ ] Invalid `maxSizeMB` values cannot produce all-pass or all-fail validation - [ ] Dev warning names the bad value and the fallback used - [ ] Production behavior stays silent and safe ## Reward I will pay **10 USDC (test tokens)** on **ARC Testnet** for a merged fix — same flow as #53, but payout is test USDC on ARC, not Base. How to claim: 1. Comment `/attempt` with this issue number before you start. 2. Open a PR referencing this issue (`Fixes #`). 3. After the PR is reviewed and merged, comment your **ARC testnet EVM address** here — you receive 10 test USDC on ARC.