Add keyboard shortcut to send requests

[arjav1528]

PR Description

This PR adds a keyboard shortcut feature that allows users to send API requests using Cmd+Enter (macOS) or Ctrl+Enter (Windows/Linux) instead of clicking the send button. This enhancement significantly improves the workflow for keyboard-centric users who prefer to navigate and interact with the application using keyboard shortcuts.

Changes Made

• Added keyboard shortcut support in RequestEditor widget (desktop view)

  • Implemented CallbackShortcuts to listen for Cmd+Enter (macOS) or Ctrl+Enter (other platforms)
  • Wrapped the editor pane with Focus widget to ensure keyboard events are properly captured
  • The shortcut triggers the same sendRequest() function used by the send button

• Added keyboard shortcut support in RequestResponsePage widget (mobile/tablet view)

  • Applied the same keyboard shortcut functionality for consistency across all views
  • Ensures the feature works seamlessly in both desktop and mobile layouts

Technical Implementation

• Uses Flutter's CallbackShortcuts widget to register keyboard bindings
• Platform-aware shortcut detection: SingleActivator with meta: true for macOS and control: true for other platforms
• Integrates with existing Riverpod state management to trigger request sending
• Maintains focus management through Focus widget with autofocus: true for immediate keyboard responsiveness

User Experience

Users can now:

1. Focus on any part of the request editor
2. Press Cmd+Enter (macOS) or Ctrl+Enter (Windows/Linux) to instantly send the request
3. Continue working without interrupting their keyboard workflow

Related Issues

• Closes Pressing command enter should send request on mac(maybe ctrl + enter on linux/windows) #935

Checklist

• I have gone through the contributing guide
• I have updated my branch and synced it with project main branch before making this PR
• I am using the latest Flutter stable branch (run flutter upgrade and verify)
• I have run the tests (flutter test) and all tests are passing

Added/updated tests?

We encourage you to add relevant test cases.

• Yes
• No, and this is why: The keyboard shortcut functionality integrates with existing widget tests. The implementation uses standard Flutter keyboard handling mechanisms (CallbackShortcuts) which are well-tested by the framework. Manual testing confirms the feature works correctly on both macOS and other platforms.

OS on which you have developed and tested the feature?

• Windows
• macOS
• Linux