Implement layout for notes and files panels and refine remove row button styling

src/styles.css

@@ -98,6 +98,20 @@ body {
   min-height: 0;
 }
 
+.notes-panel {
+  flex: 1 1 67%;
+}
+
+.files-panel {
+  flex: 0 1 33%;
+  max-height: 33%;
+}
+
+.files-panel .table {
+  flex: 1;
+  min-height: 0;
+}
+
 .panel-title {
   display: flex;
   align-items: center;
@@ -168,11 +182,11 @@ body {
 }
 
 button.remove-row-button {
-  width: 28px;
-  height: 28px;
-  min-width: 28px;
+  width: 24px;
+  height: 24px;
+  min-width: 24px;
   padding: 0;
-  border-radius: 50%;
+  border-radius: var(--control-radius);
   font-size: 12px;
   font-weight: 700;
   line-height: 1;