Add family tree page, linked from the NPC's family name

- /npcs/family/{family} (app_npc_family) renders a parent->child tree for
  everyone sharing that family name; co-parents who are both in the family
  are paired into one couple node, elders first
- FamilyTreeBuilder does the flat-list -> tree assembly
- the NPC detail page's family name (subtitle + Details row) now links there
- .family-tree CSS: nested list with connector lines, small portrait avatars

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Controller/NpcController.php

@@ -5,6 +5,7 @@ namespace App\Controller;
 use App\Entity\Npc;
 use App\Form\NpcGameNotesType;
 use App\Form\NpcType;
+use App\Npc\FamilyTreeBuilder;
 use App\Repository\NpcRepository;
 use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
@@ -66,6 +67,24 @@ class NpcController extends AbstractController
         ]);
     }
 
+    /**
+     * Family tree for one family name.
+     */
+    #[Route('/npcs/family/{family}', name: 'app_npc_family', requirements: ['family' => '[^/]+'], methods: ['GET'])]
+    public function family(string $family, NpcRepository $repo, FamilyTreeBuilder $trees): Response
+    {
+        $members = $repo->findBy(['family' => $family], ['name' => 'ASC']);
+        if (!$members) {
+            throw $this->createNotFoundException(sprintf('No NPCs in family "%s".', $family));
+        }
+
+        return $this->render('npc/family.html.twig', [
+            'family' => $family,
+            'count' => \count($members),
+            'roots' => $trees->build($members),
+        ]);
+    }
+
     /**
      * In-play detail page: everything read-only, plus the game-notes field.
      */

src/Npc/FamilyTreeBuilder.php

@@ -0,0 +1,89 @@
+<?php
+
+namespace App\Npc;
+
+use App\Entity\Npc;
+
+/**
+ * Turns a flat list of NPCs (one family) into a parent -> child tree,
+ * pairing co-parents who are both in the family into one couple node.
+ *
+ * A node is: array{npc: Npc, spouse: Npc|null, children: list<node>}
+ */
+final class FamilyTreeBuilder
+{
+    /**
+     * @param list<Npc> $members
+     *
+     * @return list<array{npc: Npc, spouse: Npc|null, children: list<array>}>
+     */
+    public function build(array $members): array
+    {
+        /** @var array<int, Npc> $byId */
+        $byId = [];
+        foreach ($members as $m) {
+            $byId[$m->getId()] = $m;
+        }
+        $inFamily = static fn (?Npc $n): bool => null !== $n && isset($byId[$n->getId()]);
+
+        // children under every in-family parent; couples via shared children
+        $childrenOf = [];
+        $spouseOf = [];
+        foreach ($members as $m) {
+            $f = $m->getFather();
+            $mo = $m->getMother();
+            foreach ([$f, $mo] as $p) {
+                if ($inFamily($p)) {
+                    $childrenOf[$p->getId()][$m->getId()] = $m;
+                }
+            }
+            if ($inFamily($f) && $inFamily($mo)) {
+                $spouseOf[$f->getId()] = $mo;
+                $spouseOf[$mo->getId()] = $f;
+            }
+        }
+
+        $done = [];   // ids emitted anywhere in the tree
+        $build = function (Npc $npc) use (&$build, $childrenOf, $spouseOf, $byId, &$done): array {
+            $done[$npc->getId()] = true;
+            $spouse = $spouseOf[$npc->getId()] ?? null;
+            if ($spouse) {
+                $done[$spouse->getId()] = true;
+            }
+
+            $kids = ($childrenOf[$npc->getId()] ?? []) + ($spouse ? ($childrenOf[$spouse->getId()] ?? []) : []);
+            uasort($kids, static fn (Npc $a, Npc $b) => ($b->getAge() ?? 0) <=> ($a->getAge() ?? 0));
+
+            $children = [];
+            foreach ($kids as $kid) {
+                if (!isset($done[$kid->getId()])) {
+                    $children[] = $build($kid);
+                }
+            }
+
+            return ['npc' => $npc, 'spouse' => $spouse, 'children' => $children];
+        };
+
+        // Elders first: members with no in-family parent, oldest first.
+        usort($members, static fn (Npc $a, Npc $b) => ($b->getAge() ?? 0) <=> ($a->getAge() ?? 0));
+
+        $roots = [];
+        foreach ($members as $m) {
+            if (isset($done[$m->getId()])) {
+                continue;
+            }
+            if ($inFamily($m->getFather()) || $inFamily($m->getMother())) {
+                continue;
+            }
+            $roots[] = $build($m);
+        }
+        // Anyone still unplaced (odd data): show as their own root.
+        foreach ($members as $m) {
+            if (!isset($done[$m->getId()])) {
+                $roots[] = $build($m);
+            }
+        }
+
+        return $roots;
+    }
+}