Add the Cornerstone export to Berichte

The 57 columns of the Cornerstone user import, in the given order and
spelling, offered as CSV and Excel under the Honestly report. Same
people and same filters as the full export.

Two things about the file itself, both of which would have failed
quietly. Cornerstone reads comma-separated, while toCsv writes the
semicolons and the BOM that German Excel wants -- the BOM would have
hidden inside the name of the first column, so "User ID" would have
matched nothing in the mapping. toCsv now takes the form as an argument
and keeps its old defaults; the Cornerstone form lives next to the
columns so a test can hold both. Quoting follows the delimiter now,
otherwise a comma in an address would split the row.

Dates go out day-first, matching the import setting. An ISO date is
read as a different, equally valid date and nobody notices.

Gender maps to Cornerstone's own values; anything unexpected becomes
"not specified" rather than empty, because an invalid value makes
Cornerstone reject the whole row, not just the field.

Status and Employment Status come from separate rules: somebody on
Karenz has a working account and is not working, and filling both from
one value gets one of the two wrong.

Four fields carry visible placeholders because the leading systems do
not supply their identifiers yet: Division ID, Doxis, Interflex,
LGVplus. Home Phone and Personal Email stay empty on purpose -- what
leaves the house is the business data.

Not verified against a running Cornerstone import, and not seen in a
browser; there is no database reachable here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

components/reports/ReportsPageClient.tsx

@@ -657,6 +657,27 @@ export function ReportsPageClient(props: ReportsPageClientProps) {
           </div>
         )}
 
+        {mode === "snapshot" && (
+          <div className="rounded border border-border bg-white p-4">
+            <h3 className="mb-1 text-xs font-semibold uppercase tracking-wide text-ink-muted">Cornerstone-Report</h3>
+            <p className="mb-1 text-xs text-ink-muted">
+              Die 57 Spalten des Cornerstone-Einlesens, Datum tagzuerst. Vier Felder tragen noch Platzhalter
+              (Division ID, Doxis, Interflex, LGVplus) und sind vor einem echten Lauf zu ersetzen.
+            </p>
+            <p className="mb-2 rounded bg-surface px-2 py-1.5 text-xs font-semibold text-ink-body">Status im Export: {statusExportLabel}</p>
+            <div className="flex gap-2">
+              <a href={exportHref("/api/export/cornerstone", "csv")} className={LINK_BUTTON_CLASS}>
+                <FileText className="h-4 w-4" />
+                CSV
+              </a>
+              <a href={exportHref("/api/export/cornerstone", "xlsx")} className={LINK_BUTTON_CLASS}>
+                <FileSpreadsheet className="h-4 w-4" />
+                Excel
+              </a>
+            </div>
+          </div>
+        )}
+
         {savedReports.length > 0 && (
           <div className="rounded border border-border bg-white p-4">
             <h3 className="mb-2 text-xs font-semibold uppercase tracking-wide text-ink-muted">Gespeicherte Berichte</h3>