feat: create new links directly from contact pages

Contact detail: + New Link button redirects to link form with contact context.
Contact create/edit form: inline new link rows (label/url/role) created on submit.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/contact_detail.html

@@ -52,6 +52,7 @@
             </datalist>
         </div>
         <button type="submit" class="btn btn-primary btn-sm">Add</button>
+        <a href="/links/create?contact_id={{ item.id }}" class="btn btn-ghost btn-sm">+ New Link</a>
     </form>
     {% for l in links %}
     <div class="list-row">