refactor: centralize duplicated formatDate helper

21 files defined their own local formatDate (with three different output
formats: date, datetime, datetime-seconds, and varying null fallbacks).
Replace them with a single shared helper at src/lib/format-date.ts that
takes a variant + optional fallback, preserving the exact previous output
per call site (verified identical string results).

Removes ~21 copies of the same logic. photos.tsx and media-grid.tsx keep
their epoch-ms based formatters since those are a different input shape.

Verified: tsc --noEmit clean, full test suite green (301/301).

src/app/(site)/help/tickets/page.tsx

@@ -1,4 +1,5 @@
 import { redirect } from "next/navigation";
+import { formatDate } from "@/lib/format-date";
 import { getTranslations } from "next-intl/server";
 import { createTicket } from "@/actions/help-tickets";
 import { ContentCard, EmptyState, StatBlock } from "@/components/public/ui";
@@ -7,9 +8,6 @@ import { prisma } from "@/lib/prisma";
 
 export const dynamic = "force-dynamic";
 
-function formatDate(d: Date | null): string {
-	return d ? d.toISOString().slice(0, 16).replace("T", " ") : "";
-}
 
 export default async function HelpTicketsPage() {
 	const session = await auth();
@@ -101,7 +99,7 @@ export default async function HelpTicketsPage() {
 											{t2.open ? t("statusOpen") : t("statusClosed")}
 										</span>
 									</td>
-									<td className="muted">{formatDate(t2.createdAt)}</td>
+									<td className="muted">{formatDate(t2.createdAt, "datetime", "")}</td>
 								</tr>
 							))}
 						</tbody>