Activity menu: add cellular row, replace Retry header with Clear Errors

- Adds cellular row (antenna icon) below Wi-Fi in connection status section;
  orange when active, muted when not in use
- Replaces "Retry Failed" header button in errors section with "Clear Errors"
  (destructive, calls clearErrorHistory); retry action retained in error detail sheet

Co-Authored-By: Kutesir <kutesir@provoc.ug>
Co-Authored-By: Sentry <sentry@provoc.ug>

Features/Backup/AppMenuView.swift

@@ -193,6 +193,31 @@ struct AppMenuView: View {
                 .padding(.horizontal, AppTheme.cardPad)
                 .padding(.vertical, 14)
 
+                menuHairline
+
+                // Cellular row
+                HStack(spacing: 12) {
+                    iconBadge("antenna.radiowaves.left.and.right", color: lanMonitor.isOnCellular ? Color(red: 1.0, green: 0.58, blue: 0.0) : AppTheme.inkSecondary)
+
+                    VStack(alignment: .leading, spacing: 2) {
+                        Text("Cellular")
+                            .font(AppTheme.body())
+                            .foregroundStyle(AppTheme.ink)
+                        Text(lanMonitor.isOnCellular ? "Active" : "Not in use")
+                            .font(AppTheme.micro())
+                            .foregroundStyle(AppTheme.inkTertiary)
+                    }
+
+                    Spacer()
+
+                    statusBadge(
+                        label: lanMonitor.isOnCellular ? "Active" : "Off",
+                        color: lanMonitor.isOnCellular ? Color(red: 1.0, green: 0.58, blue: 0.0) : AppTheme.inkQuaternary
+                    )
+                }
+                .padding(.horizontal, AppTheme.cardPad)
+                .padding(.vertical, 14)
+
                 if lanMonitor.isTailscaleActive {
                     menuHairline
 
@@ -338,13 +363,13 @@ struct AppMenuView: View {
             HStack {
                 menuSectionLabel("ERRORS")
                 Spacer()
-                if !engine.job.status.isActive {
+                if !errorEntries.isEmpty {
                     Button {
-                        retryBackup()
+                        store.clearErrorHistory()
                     } label: {
-                        Label("Retry Failed", systemImage: "arrow.clockwise")
+                        Label("Clear Errors", systemImage: "trash")
                             .font(.system(size: 11, weight: .medium))
-                            .foregroundStyle(AppTheme.interactive)
+                            .foregroundStyle(AppTheme.destructive)
                     }
                 }
             }