The 285-line _HTML string literal in edit/server.py is replaced by a
template file loaded at request time. The route handler is unchanged in
behaviour — it still substitutes __SITE_URL__, __SPORT_OPTIONS__, and
__STAT_CHECKBOXES__ before returning the response.
Five new tests cover: 200 response, form presence, site_url injection,
no unresolved placeholders, and template file existence on disk.
ALLOWED_IMAGE_TYPES, MAX_IMAGE_BYTES, and unique_image_name() were
duplicated identically in both the edit and serve servers. Centralising
them means a single change point for any future extension (e.g. adding
image/avif support).
Tests added in tests/test_shared_images.py cover no-collision, single
and chained collisions, no-suffix filenames, and constant values.
Davide Scaini