feat(db): add community_blocks table with proper DID validation master
Create migration for community blocking feature with: - user_did and community_did with widened regex validation - blocked_at timestamp for chronological ordering - record_uri and record_cid for atProto federation - Unique constraint on (user_did, community_did) pairs - Indexes for efficient queries DID regex pattern ^did:(plc|web):[a-zA-Z0-9._:%-]+$ supports: - Uppercase and lowercase letters - Dots for did:web domains (e.g., did:web:coves.social) - Hyphens, underscores, colons, percent signs per DID spec - Anchored to end for strict matching Fixes: PR review comment #1 (P0 - Critical) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>