fix(ios): handle empty NDEF tags without waiting for timeout

[samuelkchris]

Summary

• NFCError Code 403 ("NDEF tag does not contain any NDEF message") was being treated as a fatal error, causing tags to be silently skipped
• Users had to wait for the session timeout before receiving any feedback when scanning empty tags
• This fix treats error 403 as a valid tag state with nil cached NDEF message, allowing immediate user feedback

Changes

• Modified ios/Classes/NfcManagerPlugin.swift to check for NFCError Code 403 specifically
• When error 403 is encountered, the tag is returned with nil cachedNdefMessage instead of being silently skipped

Test plan

• Scan an empty NDEF tag on iOS - should trigger onDiscovered callback immediately with nil NDEF message
• Scan a tag with NDEF content - should work as before
• Verify other NFC errors are still handled correctly

Fixes #259