fix(ui): persist active request pane tab state

[AmmarKazi]

Description

Closes #8774

This PR addresses a UX friction point where switching between requests causes the Request Pane to "forget" the user's active tab and setting it to the last one used by another request.

Changes:

• Implemented useLocalStorage in RequestPane.tsx to persist the activeTab state.
• State is keyed by requestId (e.g., request-tab-selection:req_123), ensuring every request maintains its own independent context.
• The state persists across app restarts, improving workflow continuity for users working with complex request setups.

Testing Instructions

1. Open Request A and select the "Body" tab.
2. Switch to Request B and select the "Headers" tab.
3. Switch back to Request A.
   • Expected: The view immediately restores the "Body" tab.
4. Switch back to Request B.
   • Expected: The view immediately restores the "Headers" tab.
5. Close and reopen Insomnia.
   • Expected: The tab selections for both requests remain persisted.

Screen.Recording.2025-12-12.at.8.49.43.PM.mov