feat(capture): support multiline thoughts and tasks with Shift+Enter in quick dump bar

frontend/src/index.css

@@ -84,6 +84,12 @@ body {
     border-radius: 9999px !important;
   }
 
+  /* Quick-Capture-Blase bei mehrzeiliger Eingabe (Shift+Enter) */
+  .capture-bar-multiline,
+  .capture-bar-multiline.bg-panel.border {
+    border-radius: 18px !important;
+  }
+
   /* Aufgaben-Checkboxen */
   .checkbox-square {
     border-radius: var(--radius-checkbox);