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/index.html

@@ -281,6 +281,7 @@
         <button type="button" id="pedigree-back" class="ghost icon-btn" aria-label="Back to tracker" title="Back">←</button>
         <h1>🌳 Pedigree</h1>
         <div class="ped-controls">
+          <button type="button" id="ped-view" class="ghost">Fan view</button>
           <button type="button" id="ped-foldall" class="ghost">Collapse all</button>
           <div class="ped-zoom" role="group" aria-label="Zoom">
             <button type="button" id="ped-zoom-out" class="ghost icon-btn" aria-label="Zoom out" title="Zoom out">−</button>
@@ -301,6 +302,7 @@
         <div id="pedigree-subject" class="pedigree-subject" hidden></div>
         <p id="pedigree-repeat-note" class="muted-note pedigree-repeat-note" hidden>Some ancestors appear in more than one place further back (pedigree collapse). Expand the tree to reveal their ×N badges, then tap one to highlight every spot that dog appears.</p>
         <div id="pedigree-tree" class="pedigree-tree"></div>
+        <p id="pedigree-caption" class="pedigree-caption" hidden></p>
       </main>
     </div><!-- /#pedigree-screen -->