Implement proper disk and memory quota detection

Replace misleading system total quotas with actual service-specific
quota detection. Services now only show quotas when real limits exist.

Changes:
- Add get_service_disk_quota method with filesystem quota detection
- Add check_filesystem_quota and docker storage quota helpers
- Remove automatic assignment of system totals as fake quotas
- Update dashboard formatting to show usage only when no quota exists

Display behavior:
- Services with real limits: "2.1/8.0" (usage/quota)
- Services without limits: "2.1" (usage only)

This provides accurate monitoring instead of misleading system capacity
values that suggested all services had massive quotas.

dashboard/src/ui/services.rs

@@ -141,6 +141,7 @@ fn format_memory_value(used: f32, quota: f32) -> String {
     let used_gb = used / 1000.0;
     let quota_gb = quota / 1000.0;
     
+    // Show usage/quota format only if quota exists, otherwise just usage
     if quota > 0.05 {
         format!("{:.1}/{:.1}", used_gb, quota_gb)
     } else if used > 0.05 {
@@ -159,7 +160,11 @@ fn format_cpu_value(cpu_percent: f32) -> String {
 }
 
 fn format_disk_value(used: f32, quota: f32) -> String {
-    // Always show in GB format with usage/quota, no units (units in column header)
-    format!("{:.1}/{:.1}", used, quota)
+    // Show usage/quota format only if quota exists, otherwise just usage
+    if quota > 0.05 {
+        format!("{:.1}/{:.1}", used, quota)
+    } else {
+        format!("{:.1}", used)
+    }
 }