fix(journey-item-row): restore note state and show error when remove patch fails

handleNoteRemove mutated UI state optimistically without try/catch.
A failed PATCH left the note visually deleted while it survived on the
server. Now uses snapshot/rollback identical to handleNoteBlur.

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

frontend/src/lib/geschichte/JourneyItemRow.svelte

@@ -43,10 +43,18 @@ async function handleNoteBlur() {
 }
 
 async function handleNoteRemove() {
+	const prevDraft = noteDraft;
+	const prevShowNote = showNote;
 	noteDraft = '';
 	showNote = false;
 	noteError = '';
-	await onNotePatch(null);
+	try {
+		await onNotePatch(null);
+	} catch {
+		noteDraft = prevDraft;
+		showNote = prevShowNote;
+		noteError = m.journey_note_error();
+	}
 }
 
 function handleRemoveClick() {