Add a radial fan-chart view of the pedigree

Add a Fan / Tree toggle in the pedigree header. The fan places the dog in a
centre disc with each generation as a ring fanning outward, so up to nine
generations fit in one compact circle instead of a tree that doubles in
width every generation. Inner rings are labelled; tap any wedge for that
dog's details. Pedigree-collapse dogs keep their stable hue, and tapping one
lights up every wedge of that dog. The existing zoom applies to the fan too.

Render dispatch is factored into renderPedigree(); the collapse-highlight
now works on any element (tree card or fan wedge) carrying a data-dogkey.

src/changelog.json

@@ -1,4 +1,5 @@
 [
+  { "date": "2026-07-26", "text": "Added a fan-chart view of the pedigree (toggle it in the header): your dog at the centre with each generation fanning outward as a ring, so many generations fit at once without the tree sprawling sideways — tap a wedge for that dog, and repeated ancestors keep their colour" },
   { "date": "2026-07-26", "text": "Added a Collapse all / Expand all toggle to the pedigree, to fold the whole tree down to your dog or open every branch at once" },
   { "date": "2026-07-26", "text": "The pedigree is now zoomable — use the +/− buttons, ⌘/Ctrl-scroll, or pinch on a phone — to fit a wide tree on screen or zoom in for detail; your zoom level is remembered" },
   { "date": "2026-07-26", "text": "In the pedigree, a dog that fills more than one spot (pedigree collapse, common in a breed's older lines) now carries a ×N badge — tap it to highlight every place that dog appears in the tree" },