Add a collapse/expand-all toggle to the pedigree

A header button folds the whole tree down to just the dog or opens every
branch at once, alongside the per-dog toggles. Grouped with the zoom
controls, which the header now wraps on narrow screens.

src/changelog.json

@@ -1,4 +1,5 @@
 [
+  { "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" },
   { "date": "2026-07-26", "text": "The pedigree now reads top-down like a family tree — your dog on top with its sire and dam branching below — showing three generations at a glance, with each dog expandable to trace the line further back" },