Calculate actual cloud storage usage from available quota

When acrocmd shows "Occupied: 0 GB" (agent sync issue), calculate
actual usage by subtracting available from 50GB total quota.

Now displays:
  Used: ~19.04 GB (50GB - 30.96GB available)

This shows the real 19GB usage that appears in web console by
reverse-calculating from remaining quota (30.96 GB).

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

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

modules/backup/acronis-agent-status.sh

@@ -210,12 +210,32 @@ if command -v acrocmd >/dev/null 2>&1; then
     if [ -n "$vault_info" ]; then
         # Extract storage info from vault output
         vault_name=$(echo "$vault_info" | awk '{print $1}')
-        vault_free=$(echo "$vault_info" | awk '{print $4, $5}')
+        vault_free_val=$(echo "$vault_info" | awk '{print $4}')
+        vault_free_unit=$(echo "$vault_info" | awk '{print $5}')
         vault_occupied=$(echo "$vault_info" | awk '{print $6, $7}')
 
         echo -e "  Vault:        ${vault_name}"
+
+        # Calculate total quota (assumes 50GB plan, can be adjusted)
+        # If occupied shows 0 but we have "available", total = 50GB and used = 50 - available
+        if [ "$vault_occupied" = "0 GB" ] && [ -n "$vault_free_val" ]; then
+            # Assume 50GB total quota (Acronis personal plan default)
+            total_quota=50
+
+            # Calculate used: total - available
+            available_gb=$(echo "$vault_free_val" | sed 's/[^0-9.]//g')
+            used_gb=$(echo "$total_quota - $available_gb" | bc 2>/dev/null)
+
+            if [ -n "$used_gb" ] && [ "$used_gb" != "0" ]; then
+                echo -e "  Used:         ~${used_gb} GB (${total_quota}GB - ${available_gb}GB available)"
+            else
                 echo -e "  Used:         ${vault_occupied}"
-        echo -e "  Available:    ${vault_free}"
+            fi
+        else
+            echo -e "  Used:         ${vault_occupied}"
+        fi
+
+        echo -e "  Available:    ${vault_free_val} ${vault_free_unit}"
     else
         echo -e "  ${YELLOW}⚠${NC} No vault information available"
         echo -e "  ${DIM}(Cloud storage visible after first backup)${NC}"