Add per-recipient relationship labels in newsletter

Each featured person now carries a parenthetical label relative
to the recipient: "Jane Doe (your mother) — 45th birthday",
"Karl Müller (your 4th great-grandfather) — death". Labels are
italic, muted, and only appear when a path can be computed.

- New RelationshipPathFinder service mirrors webtrees'
  RelationshipService::getCloseRelationship BFS but with a
  configurable depth (default 14 hops ≈ 7 generations) so it
  reaches great-great-grandparents and beyond. Results are
  memoised per (recipient xref, target xref) within one
  dispatch run.
- nameFromPath() formatting is delegated to webtrees so the
  label honours the configured UI language (German, English,
  etc.) and gendered/inflected forms.
- The recipient's tree-bound Individual is looked up via
  Tree::getUserPreference(user, PREF_TREE_ACCOUNT_XREF). External
  admin-added recipients (no webtrees account, no linked record)
  silently get no labels — names render plain.
- Trade-off: the view now renders once per recipient (instead of
  once per language group), because the relationship map is
  personalised. For typical subscriber counts the extra string-
  concat cost is negligible compared to the SMTP send itself.

resources/views/email.phtml

@@ -20,7 +20,8 @@ use Illuminate\Support\Collection;
  * @var int                           $lookahead_days
  * @var int                           $historical_lookahead
  * @var int                           $generated_at
- * @var array<string,string>          $avatar_cids  xref => CID name
+ * @var array<string,string>          $avatar_cids   xref => CID name
+ * @var array<string,string>          $relationships xref => "your mother" etc. (per-recipient)
  * @var string                        $account_url
  */
 
@@ -50,14 +51,24 @@ $avatar_size = 56;
 
 // ─── Helpers ────────────────────────────────────────────────────────────
 
-$linked_name = static function (Individual $individual) use ($palette): string {
+$relationships = $relationships ?? [];
+
+$linked_name = static function (Individual $individual) use ($palette, $relationships): string {
     $name  = strip_tags($individual->fullName());
     $url   = $individual->url();
     $style = 'color:' . $palette['ink'] . ';text-decoration:none;'
         . 'border-bottom:1px solid ' . $palette['border'] . ';'
         . 'padding-bottom:1px;';
 
-    return '<a href="' . e($url) . '" style="' . $style . '">' . e($name) . '</a>';
+    $html = '<a href="' . e($url) . '" style="' . $style . '">' . e($name) . '</a>';
+
+    if (isset($relationships[$individual->xref()])) {
+        $html .= ' <span style="color:' . $palette['ink3'] . ';font-style:italic;font-weight:400;font-size:13px;">('
+            . e(strip_tags($relationships[$individual->xref()]))
+            . ')</span>';
+    }
+
+    return $html;
 };
 
 $record_label = static function (Fact $fact) use ($linked_name): string {