feat(preferences): configurable photo info attributes stored in user profile

- backend: users.preferences jsonb (migration 000004), Me returns preferences, PATCH /auth/me/preferences with validation (visible list + labels)
- frontend: gear in info section opens PhotoInfoSettingsDialog; base attribute set shown by default, remaining under ellipsis; per-attribute visibility and custom labels persisted to the profile; reset clears settings from the profile
- frontend: dialog has select-all/deselect-all icon buttons (no 'show all'); EXIF constants extracted to lib/exif.ts
- fix: render modal overlays via portal to document.body so they center in the viewport despite transformed panel/rail ancestors
- openspec: sync lightroom-workspace-ui artifacts (spec/design/proposal/tasks 9.8)

frontend/src/lib/components/PanelSection.svelte

@@ -7,10 +7,11 @@
 		id: string;
 		title: string;
 		open?: boolean;
+		actions?: Snippet;
 		children: Snippet;
 	}
 
-	let { id, title, open = true, children }: Props = $props();
+	let { id, title, open = true, actions, children }: Props = $props();
 
 	// svelte-ignore state_referenced_locally
 	let isOpen = $state(open);
@@ -28,18 +29,23 @@
 </script>
 
 <section class="border-border border-b">
-	<button
-		type="button"
-		class="text-text-muted hover:text-text flex w-full items-center justify-between gap-2 px-4 py-2.5 text-left"
-		aria-expanded={isOpen}
-		onclick={toggle}
-	>
-		<span class="text-xs font-semibold tracking-wide uppercase">{title}</span>
-		<Icon
-			name="expand_more"
-			class="size-4 shrink-0 transition-transform {isOpen ? 'rotate-180' : ''}"
-		/>
-	</button>
+	<div class="flex items-center">
+		<button
+			type="button"
+			class="text-text-muted hover:text-text flex flex-1 items-center justify-between gap-2 px-4 py-2.5 text-left"
+			aria-expanded={isOpen}
+			onclick={toggle}
+		>
+			<span class="text-xs font-semibold tracking-wide uppercase">{title}</span>
+			<Icon
+				name="expand_more"
+				class="size-4 shrink-0 transition-transform {isOpen ? 'rotate-180' : ''}"
+			/>
+		</button>
+		{#if actions}
+			<div class="flex items-center pr-3">{@render actions()}</div>
+		{/if}
+	</div>
 	{#if isOpen}
 		<div class="px-4 pb-4">{@render children()}</div>
 	{/if}