fix(import): address PR review concerns

- remove duplicate List import in AdminControllerTest
- derive skipped() from skippedFiles.size() — drop redundant int field
- use machine codes for SkippedFile.reason (INVALID_PDF_SIGNATURE, FILE_READ_ERROR)
- map reason codes to i18n strings in ImportStatusCard (de/en/es)
- replace raw amber Tailwind classes with warning semantic token
- fix <summary> accessibility: replace list-none with rotating chevron SVG
- replace <p> with <span> inside <summary> (phrasing content rule)
- extract setupOneValidOneFakeImport() helper — remove 3x copy-paste
- add lenient mock to short-file test for defensive coverage
- add IOException path test for isPdfMagicBytes

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

frontend/src/routes/admin/system/ImportStatusCard.svelte

@@ -15,6 +15,12 @@ const failureMessage = $derived(
 		? m.admin_system_import_failed_no_spreadsheet()
 		: m.admin_system_import_failed_internal()
 );
+
+function reasonLabel(code: string): string {
+	if (code === 'INVALID_PDF_SIGNATURE') return m.import_reason_invalid_pdf_signature();
+	if (code === 'FILE_READ_ERROR') return m.import_reason_file_read_error();
+	return code;
+}
 </script>
 
 <div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
@@ -49,16 +55,31 @@ const failureMessage = $derived(
 			<p class="mt-1 text-xs text-green-800">{m.admin_system_import_status_done()}</p>
 		</div>
 		{#if importStatus.skipped > 0}
-			<details class="mb-4 rounded-sm border border-amber-200 bg-amber-50 p-4 text-amber-700">
-				<summary class="cursor-pointer list-none">
-					<p data-testid="skipped-count" class="text-base font-bold">{importStatus.skipped}</p>
-					<p class="font-sans text-xs font-bold tracking-widest text-amber-800 uppercase">
-						{m.admin_system_import_skipped_label()}
-					</p>
+			<details class="mb-4 rounded-sm border border-warning/40 bg-warning/10 p-4 text-warning">
+				<summary class="flex cursor-pointer list-none items-center gap-2">
+					<svg
+						class="details-chevron h-4 w-4 shrink-0 transition-transform"
+						viewBox="0 0 16 16"
+						fill="none"
+						stroke="currentColor"
+						stroke-width="2"
+						stroke-linecap="round"
+						stroke-linejoin="round"
+					>
+						<path d="M6 4l4 4-4 4" />
+					</svg>
+					<div>
+						<span data-testid="skipped-count" class="block text-base font-bold"
+							>{importStatus.skipped}</span
+						>
+						<span class="block font-sans text-xs font-bold tracking-widest uppercase">
+							{m.admin_system_import_skipped_label()}
+						</span>
+					</div>
 				</summary>
 				<ul class="mt-3 space-y-1">
 					{#each importStatus.skippedFiles as { filename, reason } (filename)}
-						<li class="font-mono text-xs text-ink-2">{filename} — {reason}</li>
+						<li class="font-mono text-xs text-ink-2">{filename} — {reasonLabel(reason)}</li>
 					{/each}
 				</ul>
 			</details>
@@ -94,3 +115,9 @@ const failureMessage = $derived(
 		</button>
 	{/if}
 </div>
+
+<style>
+details[open] .details-chevron {
+	transform: rotate(90deg);
+}
+</style>

frontend/src/routes/admin/system/ImportStatusCard.svelte.test.ts

@@ -140,9 +140,9 @@ describe('ImportStatusCard', () => {
 					processed: 10,
 					skipped: 3,
 					skippedFiles: [
-						{ filename: 'fake.pdf', reason: 'Keine gültige PDF-Signatur' },
-						{ filename: 'other.pdf', reason: 'Keine gültige PDF-Signatur' },
-						{ filename: 'tiny.pdf', reason: 'Keine gültige PDF-Signatur' }
+						{ filename: 'fake.pdf', reason: 'INVALID_PDF_SIGNATURE' },
+						{ filename: 'other.pdf', reason: 'INVALID_PDF_SIGNATURE' },
+						{ filename: 'tiny.pdf', reason: 'INVALID_PDF_SIGNATURE' }
 					]
 				}),
 				ontrigger: () => {}
@@ -160,7 +160,7 @@ describe('ImportStatusCard', () => {
 					statusCode: 'IMPORT_DONE',
 					processed: 5,
 					skipped: 1,
-					skippedFiles: [{ filename: 'fake.pdf', reason: 'Keine gültige PDF-Signatur' }]
+					skippedFiles: [{ filename: 'fake.pdf', reason: 'INVALID_PDF_SIGNATURE' }]
 				}),
 				ontrigger: () => {}
 			}