fix: reset merge form after redirect

frontend/src/routes/persons/[id]/+page.svelte

@@ -9,20 +9,14 @@
 
     let editMode = false;
     let mergeTargetId = '';
-    let mergeTargetName = '';
     let showMergeConfirm = false;
 
-    function enterEdit() {
-        editMode = true;
-    }
+    function enterEdit() { editMode = true; }
+    function cancelEdit() { editMode = false; }
 
-    function cancelEdit() {
-        editMode = false;
-    }
+    $: if (form?.updated) { editMode = false; }
 
-    $: if (form?.updated) {
-        editMode = false;
-    }
+    $: person.id, (() => { mergeTargetId = ''; showMergeConfirm = false; })();
 </script>
 
 <div class="max-w-4xl mx-auto py-10 px-4">
@@ -135,6 +129,7 @@
     </div>
 
     <!-- Merge Section -->
+    {#key person.id}
     <div class="bg-white shadow-sm border border-brand-sand rounded-sm overflow-hidden mb-10">
         <div class="p-6 md:p-8">
             <h2 class="text-lg font-serif text-brand-navy mb-1">Person zusammenführen</h2>
@@ -195,6 +190,7 @@
             </form>
         </div>
     </div>
+    {/key}
 
     <!-- Linked Documents Section -->
     <div>