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/routes/documents/new/+page.svelte

@@ -17,6 +17,30 @@ let selectedReceivers: { id: string; firstName: string; lastName: string }[] = $
 );
 
 let parsedSuggestion = $state<FilenameParseResult>({});
+
+// Title is derived from the filename suggestion unless the user has typed something
+let titleDirty = $state(false);
+let titleOverride = $state('');
+let titleValue = $derived(
+	titleDirty ? titleOverride : (parsedSuggestion.suggestedTitle ?? titleOverride)
+);
+
+// Details panel: starts open when prefill data is present or a form error occurred.
+// Auto-opens when filename parsing finds a date/sender, but never force-closes — user
+// can always collapse the section manually.
+let detailsOpen = $state(
+	!!(
+		untrack(() => data.initialSenderId) ||
+		untrack(() => data.initialReceivers).length > 0 ||
+		untrack(() => form)?.error
+	)
+);
+
+$effect(() => {
+	if (parsedSuggestion.dateIso || senderId || selectedReceivers.length > 0) {
+		detailsOpen = true;
+	}
+});
 </script>
 
 <div class="mx-auto max-w-4xl px-4 py-8">
@@ -49,21 +73,51 @@ let parsedSuggestion = $state<FilenameParseResult>({});
 	{/if}
 
 	<form method="POST" enctype="multipart/form-data" use:enhance class="space-y-6 pb-20">
-		<WhoWhenSection
-			bind:senderId={senderId}
-			bind:selectedReceivers={selectedReceivers}
-			initialSenderName={data.initialSenderName}
-			suggestedDateIso={parsedSuggestion.dateIso ?? ''}
-			suggestedSenderName={parsedSuggestion.personName ?? ''}
-		/>
-		<DescriptionSection
-			bind:tags={tags}
-			titleRequired={true}
-			suggestedTitle={parsedSuggestion.suggestedTitle ?? ''}
-		/>
-		<TranscriptionSection />
+		<!-- File upload — prominent, at the top -->
 		<FileSectionNew onfileParsed={(r) => (parsedSuggestion = r)} />
 
+		<!-- Standalone title card -->
+		<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+			<label for="new-title" class="mb-1 block text-sm font-medium text-ink-2"
+				>{m.form_label_title()}</label
+			>
+			<input
+				id="new-title"
+				type="text"
+				name="title"
+				value={titleValue}
+				oninput={(e) => {
+					titleOverride = (e.target as HTMLInputElement).value;
+					titleDirty = true;
+				}}
+				class="block w-full rounded border border-line p-2 text-sm shadow-sm focus:border-ink focus:ring-ink"
+				placeholder="Titel eingeben…"
+			/>
+		</div>
+
+		<!-- Collapsible further details -->
+		<details
+			bind:open={detailsOpen}
+			class="group rounded-sm border border-line bg-surface shadow-sm"
+		>
+			<summary class="cursor-pointer list-none px-6 py-4">
+				<span class="text-xs font-bold tracking-widest text-ink-3 uppercase"
+					>{m.doc_more_details()}</span
+				>
+			</summary>
+			<div class="space-y-6 px-0 pb-6">
+				<WhoWhenSection
+					bind:senderId={senderId}
+					bind:selectedReceivers={selectedReceivers}
+					initialSenderName={data.initialSenderName}
+					suggestedDateIso={parsedSuggestion.dateIso ?? ''}
+					suggestedSenderName={parsedSuggestion.personName ?? ''}
+				/>
+				<DescriptionSection bind:tags={tags} hideTitle={true} />
+				<TranscriptionSection />
+			</div>
+		</details>
+
 		<!-- Sticky Save Bar -->
 		<div
 			class="sticky bottom-0 z-10 -mx-4 flex items-center justify-between border-t border-line bg-surface px-6 py-4 shadow-[0_-2px_8px_rgba(0,0,0,0.06)]"