feat(bugs): add Bluesky profile avatars and update How it works modal
- Add avatars next to handles in bug cards, detail view, responses, comments, and header
- Fetch avatars via GraphQL joins (appBskyActorProfileByDid) - no extra API calls
- Show first letter of handle as fallback when no avatar exists
- Add ring styling for logged-in user avatar in header
- Add Comments section to How it works modal
- Add Lexicons section with descriptions of each schema