buzz-db: extract community CRUD into community.rs #5

Problem

~400 lines of community operations live inline in lib.rs with no domain module:

• lookup_community_by_host, lookup_community_by_host_for_management
• is_community_active
• list_communities_owned_by, lookup_community_host
• get_community_icon, set_community_icon
• ensure_configured_community, create_community_with_owner
• archive_community_owned_by, unarchive_community_owned_by
• community_of_channel, communities_of_channels

Plus 7 related structs: CommunityRecord, EnsuredCommunityRecord, CreatedCommunityRecord, OwnedCommunityRecord, ArchivedCommunityRecord, UnarchivedCommunityRecord, CreateCommunityWithOwnerResult.

Every other domain (channels, events, reactions, workflows, etc.) has its own module file. Community is the gap.

Proposed change

Create community.rs containing:

• All community-related structs
• Free functions (or impl Db methods, per buzz-db: break up lib.rs — move impl Db methods to domain modules #2) for all community CRUD operations
• Associated tests

Priority

Medium — naturally done alongside #2 (lib.rs breakup). Creates a new module rather than just moving existing code.

🤖 AI review update (2026-08-23)

Proceed as one incremental #2 slice. Move community records, methods, SQL, tests, and datastore spans together into community.rs, with no API or behavior changes. This is a good early structural slice because the domain boundary is clear and it does not require the broader PgExecutor conversion.