feat(#68): lead new document form with file upload, all metadata optional

Restructure the "New Document" page so users can save quickly:

- FileSectionNew becomes the first element, redesigned as a prominent
  upload zone with an icon and large click target
- Title field is rendered standalone below the upload zone; it
  auto-populates from the filename (via parseFilename + stripExtension
  fallback) unless the user has already typed something
- All remaining metadata (who/when, description, transcription) moves
  into a collapsible "Weitere Details" section that auto-expands when
  URL prefill data or a form error is present, or when filename parsing
  detects a date/person
- title is no longer required — the form can be saved with only a file
- DescriptionSection gains a `hideTitle` prop for use in this layout
- `form_label_title` translation key no longer carries a hardcoded `*`;
  the asterisk is rendered by the template only when `titleRequired` is
  set (currently only the edit form)
- E2E tests added for all three scenarios from the issue

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/document/DescriptionSection.svelte

@@ -9,7 +9,8 @@ let {
 	initialDocumentLocation = '',
 	initialSummary = '',
 	titleRequired = false,
-	suggestedTitle = ''
+	suggestedTitle = '',
+	hideTitle = false
 }: {
 	tags?: string[];
 	initialTitle?: string;
@@ -17,17 +18,12 @@ let {
 	initialSummary?: string;
 	titleRequired?: boolean;
 	suggestedTitle?: string;
+	hideTitle?: boolean;
 } = $props();
 
-let titleValue = $state(untrack(() => initialTitle));
 let titleDirty = $state(false);
-
-$effect(() => {
-	const suggested = suggestedTitle;
-	if (suggested && !untrack(() => titleDirty)) {
-		titleValue = suggested;
-	}
-});
+let titleOverride = $state(untrack(() => initialTitle));
+let titleValue = $derived(titleDirty ? titleOverride : suggestedTitle || titleOverride);
 </script>
 
 <div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
@@ -36,25 +32,27 @@ $effect(() => {
 	</h2>
 
 	<div class="space-y-5">
-		<!-- Titel -->
-		<div>
-			<label for="title" class="mb-1 block text-sm font-medium text-ink-2"
-				>{m.form_label_title()}{#if titleRequired}
-					*{/if}</label
-			>
-			<input
-				id="title"
-				type="text"
-				name="title"
-				value={titleValue}
-				oninput={(e) => {
-					titleValue = (e.target as HTMLInputElement).value;
-					titleDirty = true;
-				}}
-				required={titleRequired}
-				class="block w-full rounded border border-line p-2 text-sm shadow-sm focus:border-ink focus:ring-ink"
-			/>
-		</div>
+		{#if !hideTitle}
+			<!-- Titel -->
+			<div>
+				<label for="title" class="mb-1 block text-sm font-medium text-ink-2"
+					>{m.form_label_title()}{#if titleRequired}
+						*{/if}</label
+				>
+				<input
+					id="title"
+					type="text"
+					name="title"
+					value={titleValue}
+					oninput={(e) => {
+						titleOverride = (e.target as HTMLInputElement).value;
+						titleDirty = true;
+					}}
+					required={titleRequired}
+					class="block w-full rounded border border-line p-2 text-sm shadow-sm focus:border-ink focus:ring-ink"
+				/>
+			</div>
+		{/if}
 
 		<!-- Aufbewahrungsort -->
 		<div>