web: admin surfaces so the PhotoPrism UI is never needed

- Account tab in General settings — self-service password change.
- UsersDialog (admin-only footer entry) — full /api/v1/users CRUD with
  admin-issued password reset.
- People as a fifth tag category alongside Labels/Keywords/Colors/Ratings,
  backed by /api/v1/subjects and the `person:` DSL clause.
- About tab in Library settings — version, library counts, feature chips,
  and a collapsible env-config help panel for the bits PP has no runtime
  API for (OIDC, TF, WebDAV).
- Library tab expanded with Indexer-advanced, extra Downloads checksums,
  and a Features grid that only renders keys PhotoPrism actually returns.
- Fix the SettingsDialog null-draft race the same way GeneralSettingsDialog
  already had: normalize on open, never null on close.

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

web/src/lib/components/layout/LeftSidebar.svelte

@@ -51,6 +51,7 @@
 	import HeapConvertDialog from './HeapConvertDialog.svelte';
 	import KebabMenu, { Item, Separator } from './KebabMenu.svelte';
 	import SettingsDialog from './SettingsDialog.svelte';
+	import UsersDialog from './UsersDialog.svelte';
 	import {
 		Copy,
 		Download,
@@ -63,7 +64,8 @@
 		Pencil,
 		Settings,
 		Sun,
-		Trash2
+		Trash2,
+		Users
 	} from 'lucide-svelte';
 	import { EmptyState, InlineLoader } from '$lib/components/feedback';
 
@@ -351,6 +353,10 @@
 	// admin dialog above — opened from the bottom-of-sidebar footer.
 	let generalSettingsOpen = $state(false);
 
+	// Admin-only user management dialog. Footer icon is gated on
+	// `isAdminUser` so non-admins never see the entry point.
+	let usersOpen = $state(false);
+
 	// Root-folder collapse state. Persisted to its own localStorage key so
 	// it doesn't collide with FolderTree's per-subfolder openSet. Defaults
 	// to open so first-time users see the full tree.
@@ -385,6 +391,7 @@
 	const TAG_CATEGORY_LABELS: Record<TagCategory, string> = {
 		labels: 'Labels',
 		keywords: 'Keywords',
+		people: 'People',
 		colors: 'Colors',
 		ratings: 'Ratings'
 	};
@@ -399,6 +406,10 @@
 		// Keywords sub-row's distinct-count semantics.
 		if (cat === 'labels') return configQuery.data?.count?.labels;
 		if (cat === 'keywords') return keywordsQuery.data?.length;
+		// People follows the same distinct-count semantics as Labels —
+		// `/api/v1/config.count.people` is the number of named subjects PP
+		// has clustered, surfaced eagerly without a separate /subjects fetch.
+		if (cat === 'people') return configQuery.data?.count?.people;
 		if (cat === 'ratings') return ratingsCount;
 		return colorsCount;
 	}
@@ -576,14 +587,15 @@
 	];
 
 	// Total badge for the "Tags" header row. Rolls up labels + keywords +
-	// ratings + colors. Labels flows through countPhotos (scoped); keywords/
-	// ratings/colors are library-wide marks tables and only contribute when
-	// we're in admin-without-BasePath mode (their sources don't scope).
+	// people + ratings + colors. Labels flows through countPhotos (scoped);
+	// keywords/people/ratings/colors are library-wide and only contribute
+	// when we're in admin-without-BasePath mode (their sources don't scope).
 	const tagsTotal = $derived.by<number | undefined>(() => {
 		if (labelsBadge === undefined) return undefined;
 		if (wantScoped) return labelsBadge;
 		const keywords = keywordsQuery.data?.length ?? 0;
-		return labelsBadge + keywords + ratingsCount + colorsCount;
+		const people = configQuery.data?.count?.people ?? 0;
+		return labelsBadge + keywords + people + ratingsCount + colorsCount;
 	});
 
 	const manageViews: ViewItem[] = [
@@ -1002,6 +1014,17 @@
 	>
 		<Settings class="h-3.5 w-3.5" />
 	</button>
+	{#if isAdminUser}
+		<button
+			type="button"
+			class="rounded p-1 text-muted-foreground hover:bg-accent hover:text-foreground"
+			onclick={() => (usersOpen = true)}
+			title="Users"
+			aria-label="Manage users"
+		>
+			<Users class="h-3.5 w-3.5" />
+		</button>
+	{/if}
 	<button
 		type="button"
 		class="rounded p-1 text-muted-foreground hover:bg-accent hover:text-foreground"
@@ -1020,3 +1043,6 @@
 	open={generalSettingsOpen}
 	onClose={() => (generalSettingsOpen = false)}
 />
+{#if isAdminUser}
+	<UsersDialog open={usersOpen} onClose={() => (usersOpen = false)} />
+{/if}