server: add server reference to context

server: set max upload size to 1 GiB

Stash remote address in context

Add legacy webhooks worker implementation

Expand context for work queues

server: use SO_REUSEADDR for main listener

server: add /query/api-meta.json, docs

server: incorporate queue management

Simplify server module

Add email work queue

Import GQL server interfaces from gql.sr.ht