fix(dbprovider): fix inflated storage values during backup restore

[Che-Zhu]

Summary

• fix dbprovider storage quantity parsing to keep Gi values unchanged when reading from Kubernetes
• prevent restore-created databases from inheriting inflated storage values
• fix database detail and list storage display to use the correct converted size

Root Cause

• dbprovider used scaledValue(Scale.Mega) / 1024 to convert storage quantities
• in the shared quantity implementation, Scale.Mega is decimal 10^6, not binary Mi
• that caused BinarySI values like 1Gi, 2Gi, and 3Gi to be parsed as inflated numbers such as 1.05, 2.10, and 3.15
• restore then wrote the inflated value back into the new cluster as ${storage}Gi, which made restored database storage larger than the source

Changes

• replace the storage conversion logic in storageFormatToNum and storageFormatToGi
• convert storage quantities by reading the raw quantity value and dividing by 1024^3
• keep the existing rounding behavior and fallback handling

Testing

• not run (small utility fix; verified the conversion logic manually with 1Gi, 2Gi, 3Gi, 5Gi, and 10Gi)