Add an interactive Tree view (pan/zoom genealogy chart)

Researched how FamilySearch/Geni/MyHeritage lay out trees (switchable pedigree/portrait/fan, an interactive canvas with pan/zoom + click-to-recenter, gender colors, birth-death years) and built a real Tree page on the MIT d3 library family-chart instead of a flat list. Ancestors + descendants around a focus person, click any card to recenter, drag to pan, scroll to zoom — scales to large imported trees. Tree is now the first per-tree sidebar item and the default when opening a tree; People keeps the searchable directory + add/edit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

frontend/app/trees/page.tsx

@@ -77,7 +77,7 @@ export default function TreesPage() {
             <li key={tree.id}>
               <Card className="transition-colors hover:border-bronze/50">
                 <CardContent className="flex items-center justify-between p-4">
-                  <Link href={`/trees/${tree.id}`} className="min-w-0 flex-1">
+                  <Link href={`/trees/${tree.id}/tree`} className="min-w-0 flex-1">
                     <div className="truncate font-medium">{tree.name}</div>
                     <div className="text-xs uppercase tracking-wide text-bronze">
                       {tree.visibility}