Pre-filter invalid NFC render methods in detection.

Update _findNfcRenderMethod() to only return valid render methods with required template/payload fields. This prevents UI from showing NFC options that won't work.

Changes:
- Add template/payload validation in _findNfcRenderMethod().
- Remove 'both fields' validation (ignore unknown fields per spec).
- Simplify error message for missing template field.
- Use TypeError for type validation instead of Error.
- Group declaration and validation without whitespace.
- Rename supportsNFC to supportsNfc for camelCase consistency.
- Rename _findNFCRenderMethod to _findNfcRenderMethod for camelCase consistency.
- Update tests to expect 'does not support NFC' error.
- Convert 'both fields' error test to success test.

Author: bparth24