Upload: no user-facing error when a photo is too large (FILE_TOO_LARGE)

**Summary** When a user uploads a photo that exceeds the size limit, the backend correctly rejects it, but the frontend shows nothing — no toast, no inline message. From the user's point of view the upload just silently fails and they don't know why. **Where** Event photo upload — the 'Add photos' flow on an event. **Steps to reproduce** 1. Open an event and click 'Add photos'. 2. Select a photo larger than the size limit (e.g. a ~6–8 MB phone photo). 3. Submit. **Expected** A clear, user-facing error (toast and/or inline message), e.g. 'One or more photos are too large.' — ideally naming the file and the max allowed size. **Actual** Nothing is shown. The upload fails silently on the frontend. **Evidence (network response)** The backend returns the right payload: ok: false code: FILE_TOO_LARGE message: 'One or more photos are too large.' The frontend is simply not surfacing it. **Suggested fix** On upload failure, surface the backend error to the user (map FILE_TOO_LARGE to a friendly toast + inline error on the affected file). Consider client-side size validation before upload so it fails fast and names the oversized file.