Refactor code structure for improved readability and maintainability

Fuchs/wwwroot/web/fis.req.css

@@ -542,6 +542,50 @@ table.if th.keep, table.if td.keep {
   animation: fis_spin 0.8s linear infinite;
 }
 
+/* Backend-authoritative draft editing (ADR 0006): server-side plausibility findings
+   rendered above the editor, and the change-history dialog table. */
+.edit_frm .invoice_layout .dvalidation {
+  margin: 0 0 1rem 0;
+}
+.edit_frm .invoice_layout .dvalidation.hidden {
+  display: none;
+}
+.edit_frm .invoice_layout .dvalidation .dvmsg {
+  padding: 0.4rem 0.7rem;
+  margin: 0.25rem 0;
+  border-radius: 0.2rem;
+  font-size: 0.9rem;
+  border-left: 4px solid #999;
+  background: #f5f5f5;
+}
+.edit_frm .invoice_layout .dvalidation .dvmsg.error {
+  border-left-color: #c0392b;
+  background: #fdecea;
+  color: #922;
+}
+.edit_frm .invoice_layout .dvalidation .dvmsg.warning {
+  border-left-color: #e0a800;
+  background: #fff8e1;
+  color: #7a5c00;
+}
+.edit_frm .invoice_layout .dvalidation .dvmsg.info {
+  border-left-color: #3498db;
+  background: #eaf4fb;
+  color: #1c5a82;
+}
+
+.dhist .invtbl {
+  width: 100%;
+}
+.dhist td, .dhist th {
+  padding: 0.3rem 0.6rem;
+  text-align: left;
+  vertical-align: top;
+}
+.dhist tbody tr:nth-child(even) {
+  background: #fafafa;
+}
+
 .modal-body .lstfrm {
   display: block;
   position: relative;