feat(profiles): notes shown on postcards page, save stays on current page

app/templates/postcards.html

@@ -5,6 +5,13 @@
     <h1>{{ profile.nickname }} 的明信片</h1>
     <a href="/profiles/{{ profile.id }}/postcards/new" class="btn btn-primary">+ 新明信片</a>
 </div>
+<div style="margin-bottom:1rem">
+    <form method="post" action="/profiles/{{ profile.id }}/notes" style="display:flex;align-items:flex-start;gap:.4rem">
+        <input type="hidden" name="redirect_to" value="/profiles/{{ profile.id }}/postcards">
+        <textarea name="notes" rows="1" placeholder="备注（仅自己可见）" style="flex:1;padding:.3rem .5rem;border:1px solid var(--border);border-radius:6px;font-size:.8rem;resize:none;font-family:inherit;line-height:1.4;min-height:1.6rem">{{ profile.notes }}</textarea>
+        <button type="submit" class="btn btn-sm" style="flex-shrink:0;margin-top:0">保存</button>
+    </form>
+</div>
 <div class="filter-bar">
     <form method="get" class="form-row">
         <select name="country">