NWC connection warning

[Akshanshkaushal]

Add NWC permission validation and error toast notifications

This PR improves the user experience when working with NWC (Nostr Wallet Connect) by adding validation checks for required permissions and displaying helpful error notifications.

Changes

• Added checkNwcPermissions() method that validates if the NWC connection has the required makeInvoice permission
• Implemented showToastWarning() method to display user-friendly toast notifications when errors occur
• Added permission validation on component initialization
• Improved error handling during invoice creation with NWC
• Added informative error messages that guide users to check their NWC connection permissions

Benefits

• Users will now receive clear visual feedback when their NWC connection is misconfigured
• Error messages provide actionable guidance for resolving permission issues
• Prevents silent failures when attempting to use NWC connections without proper permissions
• Improves overall user experience by making troubleshooting more intuitive

Closes #2