feat(l10n): replace legacy %@ format keys with semantic template keys

The Apple catalog carried four stringly-named passthrough keys ("%@",
"%@ · %@", "%@ %@ · %@", "%@%%") left over from the KMP port. They were
never referenced as keys — the composite strings were built inline with
hardcoded separators, so the middot/percent formatting wasn't localizable.

Renames them to proper semantic keys in strings.json:
  - format_separated_pair(first:second:)     "{first} · {second}"
  - format_separated_triple(first:second:third:)
  - battery_level_value(level:)              "{level}%"
and drops the pure-identity "%@". Wires the inline compositions (size ·
status, count files · size, receivers pending · completed, battery level)
to the generated typed accessors. Catalog now validates with zero warnings.

apple/VniDrop/Features/Receive/ReceiveScreen.swift

@@ -137,7 +137,7 @@ private struct ReceiveTransferRow: View {
 			VStack(alignment: .leading, spacing: 3) {
 				Text(transfer.transferName ?? String(localized: L10n.Receive.unknownTransfer))
 					.font(.body).lineLimit(1)
-				Text("\(formatBytes(transfer.totalSize)) · \(statusLabel(transfer.status))")
+				Text(L10n.Format.separatedPair(first: formatBytes(transfer.totalSize), second: statusLabel(transfer.status)))
 					.font(.caption).foregroundStyle(.secondary)
 				if transfer.status == .receiving, let progress {
 					ProgressRow(labelKey: progress.labelKey, progress: progress.progress, detail: progress.detail)