Add line wrap toggle for editor and paste viewer (#130)

Shared client-side preference in localStorage 'palette-wrap', default
off. Toggle button on /new editor head and paste title bar, plus a Line
wrap checkbox in the settings menu; all read/write the same preference.
Active state uses the accent treatment like other toggles. No em dashes
in UI text.

internal/web/templates/settings.html

@@ -13,6 +13,8 @@
         <svg class="icon-moon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/></svg>
         <span>Dark mode</span>
       </button>
+      <h3 style="margin-top:18px">Editor</h3>
+      <label class="toggle" for="wrap-setting" style="display:inline-flex"><input type="checkbox" id="wrap-setting"> Line wrap</label>
       <p class="admin-link-row"><a class="admin-link" href="/admin">Admin</a></p>
     </div>
   </div>