Add sighting beat type backed by iNaturalist clumps

[simonw]

Clone simonw/tools to /tmp and look at inat-sightings.html

We are going to add a new type of beat called “sightings” based on that prototype

A sighting is a group of observations (a “clump” according to the API that uses) in a single beat, rendered using that image gallery component

The blog already has a mechanism for only loading the code for a web component if it is present on the page - we will use that

These sighting beats are shown with the date and time or time range similar to the inat-sightings.html prototype

We need an importer mechanism wired up on /admin/importers too

Run tests first. Build with red/green TDD and a mocked API response

Each sighting beat is a "clump" of iNaturalist observations rendered with
a new component (a renamed copy of the prototype
in simonw/tools so the existing stays untouched). The
component lazy-loads via the existing base.html querySelector mechanism.
Time ranges (single time, same-day, cross-day) are formatted from the
clump's started_at/ended_at metadata. Imports run from /admin/importers.

https://claude.ai/code/session_018CLLDeHNykeKaCbDauGALE