Add skeleton loading states to table components

[hiirrxnn]

This PR implements skeleton loading states for all table components (Pods, Jobs, Queues) to improve user experience while data is being fetched. Users now see immediate visual feedback with placeholder content that matches the actual table structure.

Solves #143

🔧 Changes Made

Table Components Enhanced:

• JobTable: Added skeleton rows with 6 columns matching the actual structure
• PodsTable: Added skeleton rows with 5 columns matching pod data layout
• QueueTable: Added dynamic skeleton rows that adapt to allocated fields

Parent Components Updated:

• Jobs.jsx: Pass isLoading and skeletonRows props to JobTable
• Pods.jsx: Pass isLoading and skeletonRows props to PodsTable
• Queues.jsx: Pass isLoading and skeletonRows props to QueueTable

Skeleton Features:

• Realistic Layout: Different skeleton widths (60%, 70%, 80%, 90%) for natural appearance
• Proper Variants: Text skeletons for content, rounded for badges, circular for action buttons
• Smooth Transitions: No layout shifts when transitioning from skeleton to real content

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[hiirrxnn]

/assign @william-wang