feat(lexicon): add vote create and delete lexicons
Add XRPC procedure lexicons for voting on posts/comments:
- social.coves.feed.vote.create: Create/toggle votes with up/down direction
- social.coves.feed.vote.delete: Remove existing votes
Follows atproto lexicon best practices:
- Uses knownValues for direction (not closed enum)
- References com.atproto.repo.strongRef for subject
- UpperCamelCase error names per spec
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>