feat(preview): play videos inline in the lightbox overlay

Switch the preview overlay from a still <img> to a <video> tag when the
focused photo's Type is "video". Uses PhotoPrism's /api/v1/videos/:hash
endpoint with the existing previewToken, falls back to a still thumb as
the poster, and autoplays muted so the controls reveal without
clobbering whatever else is on the page.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/components/preview/PreviewOverlay.svelte

@@ -8,10 +8,10 @@
 		previewNext,
 		previewPrev
 	} from '$lib/stores/preview.svelte';
-	import { thumbUrl } from '$lib/stores/session.svelte';
+	import { thumbUrl, videoUrl } from '$lib/stores/session.svelte';
 	import { setFocused } from '$lib/stores/selection.svelte';
 	import RightSidebar from '$lib/components/sidebar/RightSidebar.svelte';
-	import { primaryFile, type PpPhoto } from '$lib/types/photoprism';
+	import { isVideo, primaryFile, videoFile, type PpPhoto } from '$lib/types/photoprism';
 
 	const photoQuery = createQuery<PpPhoto>(() => ({
 		queryKey: ['photo', preview.uid ?? ''],
@@ -141,12 +141,25 @@
 				<p class="text-sm text-red-300">Failed to load photo.</p>
 			{:else if photoQuery.data}
 				{@const pf = primaryFile(photoQuery.data)}
+				{#if isVideo(photoQuery.data)}
+					{@const vf = videoFile(photoQuery.data)}
+					<!-- svelte-ignore a11y_media_has_caption -->
+					<video
+						src={videoUrl(vf.Hash)}
+						poster={thumbUrl(pf.Hash, 'fit_1920')}
+						controls
+						autoplay
+						muted
+						class="max-h-full max-w-full rounded-md object-contain shadow-2xl"
+					></video>
+				{:else}
 					<img
 						src={thumbUrl(pf.Hash, 'fit_1920')}
 						alt={photoQuery.data.OriginalName ?? pf.Name ?? 'Photo'}
 						class="max-h-full max-w-full rounded-md object-contain shadow-2xl"
 					/>
 				{/if}
+			{/if}
 		</div>
 
 		<!-- Right: metadata sidebar -->

web/src/lib/stores/session.svelte.ts

@@ -87,3 +87,14 @@ export function thumbUrl(hash: string, size = 'tile_500'): string {
 	if (!session.previewToken) return '';
 	return `/api/v1/t/${hash}/${session.previewToken}/${size}`;
 }
+
+/**
+ * Build a video stream URL. PhotoPrism's endpoint is
+ * /api/v1/videos/:hash/:token/:format — same previewToken as thumbnails.
+ * `format=avc` is the standard h264 transcode; HEVC sources are
+ * transcoded on first request and cached server-side.
+ */
+export function videoUrl(hash: string, format = 'avc'): string {
+	if (!session.previewToken) return '';
+	return `/api/v1/videos/${hash}/${session.previewToken}/${format}`;
+}

web/src/lib/types/photoprism.ts

@@ -174,6 +174,19 @@ export function primaryFile(p: PpPhoto): PpFile {
 	};
 }
 
+export function isVideo(p: PpPhoto): boolean {
+	return p.Type === 'video';
+}
+
+/** Return the Files[] entry that carries the actual video stream. Falls back
+ *  to primaryFile() if no video MediaType is present (shouldn't happen for
+ *  Type === 'video' but keeps the call site total). */
+export function videoFile(p: PpPhoto): PpFile {
+	const files = p.Files ?? [];
+	const v = files.find((f) => f.MediaType?.startsWith('video/'));
+	return v ?? primaryFile(p);
+}
+
 export interface PpFile {
 	UID: string;
 	Hash: string;