feat(metadata,people): richer metadata editing + face-naming flow

Metadata (sidebar):
- New editable fields: Title, Credits section (Artist/Copyright/
  License via Details), GPS Altitude.
- Video facts in the File section: Duration, FPS, Codec — required
  fixing videoFile(): PhotoPrism serializes MediaType as the bare word
  "video", so the old startsWith('video/') check never matched and the
  helper always fell back to the JPEG poster.
- Timezone correctness: buildTakenAtPatch no longer forces
  TakenAtLocal=UTC; it preserves the photo's existing UTC↔local offset
  (per-photo in bulk edits) so PhotoPrism can't clobber manual date
  edits when recomputing from TimeZone, and Year/Month/Day now derive
  from local wall-clock time.

People (was "disabled" — really: zero subjects because naming is what
creates a person, and the UI had no naming flow; prod has 40k face
markers in 790 unnamed clusters):
- Sidecar GET /api/sidecar/subjects — scoped people list via one
  markers→files→photos SQL pass (labels pattern), replacing the
  client-side probe-per-subject N+1 filter.
- Sidecar GET /api/sidecar/faces/unnamed — the caller's unnamed face
  clusters with count, crop thumb, and a representative marker UID.
- "Name new faces" panel on /tags/people: face-crop cards with inline
  name input; naming uses PhotoPrism's own flow (PUT /markers/:uid
  {Name, SubjSrc:manual}, verified against PP source) which creates
  the Subject and propagates across the cluster.
- Scoped proxy: marker PUT / subject-clear DELETE now allowed with
  per-marker ownership checks (was blanket-forbidden, which would have
  blocked naming for scoped users).
- Per-photo People chips in the sidebar from named Files[].Markers,
  linking to the person's page.

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

web/src/lib/components/people/NewFacesPanel.svelte

@@ -0,0 +1,112 @@
+<!--
+	"Name new faces" — the missing half of the People feature. PhotoPrism
+	only creates a person once someone names a detected face cluster, so a
+	library can have tens of thousands of face markers and still show an
+	empty People list. This panel surfaces the caller's unnamed clusters
+	(scoped server-side to their BasePath) as face-crop cards with an
+	inline name input; naming goes through PhotoPrism's own flow (PUT on
+	the cluster's representative marker), which creates the Subject and
+	propagates it across the cluster.
+-->
+<script lang="ts">
+	import { createQuery, useQueryClient } from '@tanstack/svelte-query';
+	import { toast } from 'svelte-sonner';
+	import {
+		listUnnamedFaces,
+		nameFaceCluster,
+		type UnnamedFaceCluster
+	} from '$lib/services/photoprism';
+	import { isAuthenticated, thumbUrl } from '$lib/stores/session.svelte';
+	import { InlineLoader } from '$lib/components/feedback';
+	import { UserPlus } from 'lucide-svelte';
+
+	const qc = useQueryClient();
+
+	const facesQuery = createQuery<UnnamedFaceCluster[]>(() => ({
+		queryKey: ['faces', 'unnamed'],
+		queryFn: listUnnamedFaces,
+		enabled: isAuthenticated(),
+		staleTime: 60_000
+	}));
+
+	let drafts = $state<Record<string, string>>({});
+	let busy = $state<Record<string, boolean>>({});
+
+	async function submit(cluster: UnnamedFaceCluster) {
+		const name = (drafts[cluster.faceId] ?? '').trim();
+		if (!name || busy[cluster.faceId]) return;
+		busy[cluster.faceId] = true;
+		try {
+			await nameFaceCluster(cluster.markerUid, name);
+			toast.success(`Named ${name}`, {
+				description:
+					'PhotoPrism links the whole cluster in the background — the photo count may keep growing.'
+			});
+			drafts[cluster.faceId] = '';
+			void qc.invalidateQueries({ queryKey: ['faces', 'unnamed'] });
+			void qc.invalidateQueries({ queryKey: ['subjects'] });
+		} catch (err) {
+			toast.error(err instanceof Error ? err.message : 'Naming failed');
+		} finally {
+			busy[cluster.faceId] = false;
+		}
+	}
+
+	const clusters = $derived(facesQuery.data ?? []);
+</script>
+
+{#if facesQuery.isPending}
+	<InlineLoader label="Looking for unnamed faces…" />
+{:else if clusters.length > 0}
+	<section class="space-y-3">
+		<header class="space-y-0.5">
+			<h2 class="flex items-center gap-1.5 text-sm font-medium text-foreground">
+				<UserPlus class="h-4 w-4" /> Name new faces
+			</h2>
+			<p class="text-[11px] text-muted-foreground">
+				Faces PhotoPrism detected but nobody has named yet. Naming one creates a person and tags
+				every matching photo.
+			</p>
+		</header>
+		<div
+			class="grid gap-3"
+			style="grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));"
+		>
+			{#each clusters as cluster (cluster.faceId)}
+				<div
+					class="flex flex-col items-center gap-2 rounded-md border border-border bg-card/30 p-3"
+				>
+					<div class="relative">
+						<img
+							src={thumbUrl(cluster.thumb, 'tile_224')}
+							alt="Unnamed face"
+							loading="lazy"
+							decoding="async"
+							class="h-20 w-20 rounded-full border border-border object-cover"
+						/>
+						<span
+							class="absolute -bottom-1 -right-1 rounded-full bg-secondary px-1.5 py-0.5 text-[10px] font-medium tabular-nums text-muted-foreground"
+							title={`${cluster.count} of your photos carry this face`}
+						>
+							{cluster.count}
+						</span>
+					</div>
+					<input
+						type="text"
+						placeholder="Name…"
+						disabled={busy[cluster.faceId]}
+						class="w-full rounded border border-input bg-background px-1.5 py-1 text-center text-xs shadow-sm focus:outline-none focus:ring-1 focus:ring-ring disabled:opacity-50"
+						bind:value={drafts[cluster.faceId]}
+						onkeydown={(e) => {
+							if (e.key === 'Enter') {
+								e.preventDefault();
+								void submit(cluster);
+							}
+						}}
+						onblur={() => void submit(cluster)}
+					/>
+				</div>
+			{/each}
+		</div>
+	</section>
+{/if}