aa5e7f95

By: Michael Lynch <git@mtlynch.io>

Simplify upload handler after code review

- Drop duplicate CreateMediaItem; reuse existing InsertMediaItem.
- Reuse mediastore.WriteConverted for the full-size strip-and-write path
  instead of hand-rolled temp-file plumbing.
- Make MaxBytesReader the single photo-size limit and return a real 413
  on overflow; drop the unreachable byte-size check in NewProcessablePhoto.
- Inline the no-op NewFilename wrapper and collapse repeated file.Close()
  in parseUploadPostRequest; remove the now-redundant internal test
  (empty-filename rejection is covered in little_moments/media_test.go).
- Document the files-before-DB-row ordering choice.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>