feat(ui-loader): loader for sendButton transactions

[dhananjaypai08]

Summary

This PR introduces a reusable Loader component and integrates it into the SendButton workflow to enhance UX feedback during async operations. The spinner replaces button text during loading states like approvals and transfers, giving users a clear visual cue that a process is underway.

Note : This can be further used for connectWallet and other components

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Changes Introduced

• Created a lightweight, reusable Loader component (Loader.tsx) using Tailwind for consistent styling within the packages/ccip-react-components/lib

• Integrated Loader in the SendButton:

  • During token approval (Approve)
  • During LINK/fee token approval (Approve LINK)
  • During token transfer (Send)

• Replaced button text dynamically with the spinner during each respective async mutation’s pending state (isPending).

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Why This Change?

• Improves user feedback and perception of responsiveness during blockchain interactions.
• Reduces the risk of duplicate submissions by visibly indicating loading states.
• Keeps UX consistent and clean with reusable visual feedback across components.