fix(export-ui): indicate the selected format and default to xlsx

Radio.Card's only checked cue is a border tint, which is invisible at the
p="xs" the three format cards use — so the dialog gave no sign of which
format was picked. ReportExportButton's cards already carry a
Radio.Indicator; this adds the same one, dropped when the card was
compressed to an icon-over-label stack.

Default is now xlsx rather than csv: typed number and date columns mean a
spreadsheet opens it without the "is this text?" pass. It falls back to
dataset.formats[0] so the dialog can never preset a format the dataset
does not offer.

That default also made the over-cap alert misleading. It suggested
switching to CSV whenever the format was not CSV, but CSV_ROW_CAP and
XLSX_ROW_CAP are both 50_000 — from the new default that buys nothing.
It is now gated on dataset.caps.csv > cap, so it appears only from PDF,
where the cap really is lower.

apps/edr-freight-web/backoffice/src/components/export/ExportDialog.tsx

@@ -67,7 +67,12 @@ export function ExportDialog({ opened, onClose, dataset, params }: ExportDialogP
   );
 
   const [selected, setSelected] = useState<string[]>(defaultKeys);
-  const [format, setFormat] = useState<ExportFormat>("csv");
+  // xlsx by default: typed number and date columns, so a spreadsheet opens it
+  // without the "is this text?" pass CSV needs. Falls back to whatever the
+  // dataset does offer rather than presetting a format it would reject.
+  const [format, setFormat] = useState<ExportFormat>(
+    () => (dataset.formats.includes("xlsx") ? "xlsx" : dataset.formats[0]),
+  );
   const [scope, setScope] = useState("all");
   const [search, setSearch] = useState("");
   const [exporting, setExporting] = useState(false);
@@ -343,7 +348,15 @@ export function ExportDialog({ opened, onClose, dataset, params }: ExportDialogP
                       return (
                         <Radio.Card key={f} value={f} radius="md" p="xs">
                           <Stack gap={4} align="center">
-                            <Icon size={18} />
+                            {/* Radio.Card's own checked state is a border tint
+                                and nothing else, which reads as unselected at
+                                this size. The Indicator is what actually says
+                                which format is picked, as the report export
+                                dialog's cards already do. */}
+                            <Group gap={6} wrap="nowrap">
+                              <Radio.Indicator size="xs" />
+                              <Icon size={18} />
+                            </Group>
                             <Text size="xs" fw={500}>
                               {label}
                             </Text>
@@ -385,7 +398,7 @@ export function ExportDialog({ opened, onClose, dataset, params }: ExportDialogP
                   <Text size="xs">
                     {total?.toLocaleString()} rows exceeds the {cap.toLocaleString()}-row{" "}
                     {FORMAT_META[format].label} limit. Narrow the filters
-                    {format !== "csv" ? ", switch to CSV," : ""} or{" "}
+                    {dataset.caps.csv > cap ? ", switch to CSV," : ""} or{" "}
                     <Anchor size="xs" onClick={() => setScope(String(cap))}>
                       export the first {cap.toLocaleString()}
                     </Anchor>