fix(ui): cross-module mechanical unifications (line-item labels/align, back-tab targets, status-button colors, apply_vat checkbox, currency-from-settings, read-only issued_by, Celkem header, centered offer tabs)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/Offers.tsx

@@ -741,7 +741,7 @@ export default function Offers() {
         }
       />
 
-      <Box sx={{ mb: 2.5 }}>
+      <Box sx={{ display: "flex", justifyContent: "center", mb: 2.5 }}>
         <Tabs
           value={statusFilter}
           onChange={(v) => {