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)/radio/contests/[id]/page.tsx

@@ -1,4 +1,5 @@
 import Link from "next/link";
+import { formatDate } from "@/lib/format-date";
 import { notFound } from "next/navigation";
 import { getTranslations } from "next-intl/server";
 import { ContentCard } from "@/components/public/ui";
@@ -6,9 +7,6 @@ import { prisma } from "@/lib/prisma";
 
 export const revalidate = 300;
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 19).replace("T", " ") : "";
-}
 
 export default async function RadioContestDetailPage({
 	params,
@@ -63,15 +61,15 @@ export default async function RadioContestDetailPage({
 						<tr>
 							<th>Period</th>
 							<td>
-								{contest.startDate ? formatDate(contest.startDate) : "—"}
+								{contest.startDate ? formatDate(contest.startDate, "datetime-seconds", "") : "—"}
 								{" — "}
-								{contest.endDate ? formatDate(contest.endDate) : "ongoing"}
+								{contest.endDate ? formatDate(contest.endDate, "datetime-seconds", "") : "ongoing"}
 							</td>
 						</tr>
 						<tr>
 							<th>Created</th>
 							<td>
-								{formatDate(contest.createdAt) || (
+								{formatDate(contest.createdAt, "datetime-seconds", "") || (
 									<span className="muted">—</span>
 								)}
 							</td>
@@ -79,7 +77,7 @@ export default async function RadioContestDetailPage({
 						<tr>
 							<th>Updated</th>
 							<td>
-								{formatDate(contest.updatedAt) || (
+								{formatDate(contest.updatedAt, "datetime-seconds", "") || (
 									<span className="muted">—</span>
 								)}
 							</td>

src/app/(site)/radio/contests/page.tsx

@@ -1,13 +1,11 @@
 import Link from "next/link";
+import { formatDate } from "@/lib/format-date";
 import { getTranslations } from "next-intl/server";
 import { ContentCard, EmptyState } from "@/components/public/ui";
 import { prisma } from "@/lib/prisma";
 
 export const revalidate = 300;
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 10) : "";
-}
 
 export default async function RadioContestsPage() {
 	const t = await getTranslations("pages.radioContests");
@@ -67,7 +65,7 @@ export default async function RadioContestsPage() {
 										style={{ margin: 0, fontSize: "0.85rem" }}
 									>
 										{c.startDate
-											? `${formatDate(c.startDate)} — ${c.endDate ? formatDate(c.endDate) : "ongoing"}`
+											? `${formatDate(c.startDate, "date", "")} — ${c.endDate ? formatDate(c.endDate, "date", "") : "ongoing"}`
 											: t("dateUnknown")}
 									</p>
 								</Link>

src/app/(site)/radio/giveaways/[id]/page.tsx

@@ -1,4 +1,5 @@
 import Link from "next/link";
+import { formatDate } from "@/lib/format-date";
 import { notFound } from "next/navigation";
 import { getTranslations } from "next-intl/server";
 import { ContentCard } from "@/components/public/ui";
@@ -6,9 +7,6 @@ import { prisma } from "@/lib/prisma";
 
 export const revalidate = 300;
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 19).replace("T", " ") : "";
-}
 
 export default async function RadioGiveawayDetailPage({
 	params,
@@ -68,15 +66,15 @@ export default async function RadioGiveawayDetailPage({
 						<tr>
 							<th>Period</th>
 							<td>
-								{giveaway.startDate ? formatDate(giveaway.startDate) : "—"}
+								{giveaway.startDate ? formatDate(giveaway.startDate, "datetime-seconds", "") : "—"}
 								{" — "}
-								{giveaway.endDate ? formatDate(giveaway.endDate) : "ongoing"}
+								{giveaway.endDate ? formatDate(giveaway.endDate, "datetime-seconds", "") : "ongoing"}
 							</td>
 						</tr>
 						<tr>
 							<th>Created</th>
 							<td>
-								{formatDate(giveaway.createdAt) || (
+								{formatDate(giveaway.createdAt, "datetime-seconds", "") || (
 									<span className="muted">—</span>
 								)}
 							</td>
@@ -84,7 +82,7 @@ export default async function RadioGiveawayDetailPage({
 						<tr>
 							<th>Updated</th>
 							<td>
-								{formatDate(giveaway.updatedAt) || (
+								{formatDate(giveaway.updatedAt, "datetime-seconds", "") || (
 									<span className="muted">—</span>
 								)}
 							</td>

src/app/(site)/radio/giveaways/page.tsx

@@ -1,13 +1,11 @@
 import Link from "next/link";
+import { formatDate } from "@/lib/format-date";
 import { getTranslations } from "next-intl/server";
 import { ContentCard, EmptyState } from "@/components/public/ui";
 import { prisma } from "@/lib/prisma";
 
 export const revalidate = 300;
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 10) : "";
-}
 
 export default async function RadioGiveawaysPage() {
 	const t = await getTranslations("pages.radioGiveaways");
@@ -74,7 +72,7 @@ export default async function RadioGiveawaysPage() {
 										style={{ margin: 0, fontSize: "0.85rem" }}
 									>
 										{g.startDate
-											? `${formatDate(g.startDate)} — ${g.endDate ? formatDate(g.endDate) : "ongoing"}`
+											? `${formatDate(g.startDate, "date", "")} — ${g.endDate ? formatDate(g.endDate, "date", "") : "ongoing"}`
 											: t("dateUnknown")}
 									</p>
 								</Link>

src/app/(site)/radio/requests/page.tsx

@@ -1,4 +1,5 @@
 import { getTranslations } from "next-intl/server";
+import { formatDate } from "@/lib/format-date";
 import { submitRequest } from "@/actions/radio-requests";
 import { ContentCard, EmptyState } from "@/components/public/ui";
 import { auth } from "@/lib/auth";
@@ -6,9 +7,6 @@ import { prisma } from "@/lib/prisma";
 
 export const dynamic = "force-dynamic";
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 16).replace("T", " ") : "";
-}
 
 export default async function RadioRequestsPage() {
 	const t = await getTranslations("pages.radioRequests");
@@ -136,7 +134,7 @@ export default async function RadioRequestsPage() {
 											)}
 										</td>
 										<td className="muted">
-											{r.submittedAt ? formatDate(r.submittedAt) : "—"}
+											{r.submittedAt ? formatDate(r.submittedAt, "datetime", "") : "—"}
 										</td>
 										<td>{status}</td>
 									</tr>

src/app/(site)/radio/shouts/page.tsx

@@ -1,4 +1,5 @@
 import { getTranslations } from "next-intl/server";
+import { formatDate } from "@/lib/format-date";
 import { postShout } from "@/actions/radio-shouts";
 import { ContentCard, EmptyState } from "@/components/public/ui";
 import { auth } from "@/lib/auth";
@@ -8,9 +9,6 @@ import { siteSettings } from "@/lib/services/site-settings";
 
 export const dynamic = "force-dynamic";
 
-function formatDate(d: Date | null | undefined): string {
-	return d ? d.toISOString().slice(0, 16).replace("T", " ") : "";
-}
 
 export default async function RadioShoutsPage() {
 	const t = await getTranslations("pages.radioShouts");
@@ -124,7 +122,7 @@ export default async function RadioShoutsPage() {
 									<div style={{ flex: 1, minWidth: 0 }}>
 										<p style={{ margin: "0 0 0.25rem" }}>
 											<strong>{author?.username ?? `User #${s.userId}`}</strong>{" "}
-											<span className="muted">{formatDate(s.createdAt)}</span>
+											<span className="muted">{formatDate(s.createdAt, "datetime", "")}</span>
 										</p>
 										<p style={{ margin: 0 }}>{s.message}</p>
 									</div>