fix: exclude storage_size from job list serializer

[erick-GeGe]

Description

• Remove storage_size calculation from SpiderJobSerializer (used in list endpoints)
• Add SpiderJobDetailSerializer that includes storage_size, used only in job retrieve
• Prevents collStats being called N×3 times per list request, which was exhausting MongoDB file descriptors with 30k+ collections

Issue

• Github Issue ID.

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