Add retry button for individual failed sensors on results screen

- Added handleRetryFromResults function to retry setup for a single sensor
- Added Retry button next to each failed/skipped sensor in the results list
- When clicked, resets sensor state and returns to batch setup phase
- Added new styles: resultItemWithAction, resultItemLeft, retryItemButton

TASK-6.2: Add results screen after batch setup

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/(tabs)/beneficiaries/[id]/setup-wifi.tsx

@@ -433,6 +433,23 @@ export default function SetupWiFiScreen() {
     router.replace(`/(tabs)/beneficiaries/${id}/equipment` as any);
   };
 
+  // Retry a single sensor from results screen
+  const handleRetryFromResults = (deviceId: string) => {
+    const index = sensors.findIndex(s => s.deviceId === deviceId);
+    if (index >= 0) {
+      // Reset the sensor state
+      setSensors(prev => prev.map(s =>
+        s.deviceId === deviceId
+          ? { ...s, status: 'pending' as SensorSetupStatus, error: undefined, steps: createInitialSteps() }
+          : s
+      ));
+      setCurrentIndex(index);
+      setIsPaused(false);
+      // Go back to batch setup phase
+      setPhase('batch_setup');
+    }
+  };
+
   const getSignalStrength = (rssi: number): string => {
     if (rssi >= -50) return 'Excellent';
     if (rssi >= -60) return 'Good';
@@ -507,21 +524,30 @@ export default function SetupWiFiScreen() {
             <View style={styles.resultsSection}>
               <Text style={styles.resultsSectionTitle}>Failed</Text>
               {failedSensors.map(sensor => (
-                <View key={sensor.deviceId} style={styles.resultItem}>
-                  <Ionicons
-                    name={sensor.status === 'skipped' ? 'remove-circle' : 'close-circle'}
-                    size={20}
-                    color={sensor.status === 'skipped' ? AppColors.warning : AppColors.error}
-                  />
-                  <View style={styles.resultItemContent}>
-                    <Text style={styles.resultItemText}>{sensor.deviceName}</Text>
-                    {sensor.error && (
-                      <Text style={styles.resultItemError}>{sensor.error}</Text>
-                    )}
-                    {sensor.status === 'skipped' && (
-                      <Text style={styles.resultItemError}>Skipped</Text>
-                    )}
+                <View key={sensor.deviceId} style={styles.resultItemWithAction}>
+                  <View style={styles.resultItemLeft}>
+                    <Ionicons
+                      name={sensor.status === 'skipped' ? 'remove-circle' : 'close-circle'}
+                      size={20}
+                      color={sensor.status === 'skipped' ? AppColors.warning : AppColors.error}
+                    />
+                    <View style={styles.resultItemContent}>
+                      <Text style={styles.resultItemText}>{sensor.deviceName}</Text>
+                      {sensor.error && (
+                        <Text style={styles.resultItemError}>{sensor.error}</Text>
+                      )}
+                      {sensor.status === 'skipped' && (
+                        <Text style={styles.resultItemError}>Skipped</Text>
+                      )}
+                    </View>
                   </View>
+                  <TouchableOpacity
+                    style={styles.retryItemButton}
+                    onPress={() => handleRetryFromResults(sensor.deviceId)}
+                  >
+                    <Ionicons name="refresh" size={16} color={AppColors.primary} />
+                    <Text style={styles.retryItemButtonText}>Retry</Text>
+                  </TouchableOpacity>
                 </View>
               ))}
             </View>
@@ -1039,6 +1065,20 @@ const styles = StyleSheet.create({
     paddingVertical: Spacing.xs,
     gap: Spacing.sm,
   },
+  resultItemWithAction: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    justifyContent: 'space-between',
+    paddingVertical: Spacing.sm,
+    borderBottomWidth: 1,
+    borderBottomColor: AppColors.border,
+  },
+  resultItemLeft: {
+    flexDirection: 'row',
+    alignItems: 'flex-start',
+    flex: 1,
+    gap: Spacing.sm,
+  },
   resultItemContent: {
     flex: 1,
   },
@@ -1052,6 +1092,20 @@ const styles = StyleSheet.create({
     color: AppColors.error,
     marginTop: 2,
   },
+  retryItemButton: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    gap: Spacing.xs,
+    paddingVertical: Spacing.xs,
+    paddingHorizontal: Spacing.sm,
+    backgroundColor: AppColors.primaryLighter,
+    borderRadius: BorderRadius.md,
+  },
+  retryItemButtonText: {
+    fontSize: FontSizes.sm,
+    fontWeight: FontWeights.semibold,
+    color: AppColors.primary,
+  },
   bottomActions: {
     padding: Spacing.lg,
     borderTopWidth: 1,