Adds BaseItemDto, QueryResult, UserItemDataDto, UserDto,
AuthenticationResult, MediaSourceInfo, PlaybackInfoResponse,
NameGuidPair and SessionInfo DTOs to server/jellyfin/dto, plus
model-to-DTO mappers for songs, albums, artists and genres that
later browse/stream/write endpoints will consume.
Add jellyfin.New to the shared Wire provider set and a
CreateJellyfinAPIRouter injector, then mount the router at /jellyfin
in startServer(), gated by conf.Server.Jellyfin.Enabled, mirroring the
existing LastFM/ListenBrainz router mounts.
Adds server/jellyfin: the Router (mirrors server/subsonic and
server/public), its Wire-friendly New(...) constructor, a chi routes()
table, and the ok() JSON response helper. Implements the unauthenticated
handshake surface Jellyfin clients probe first: GET /System/Info/Public,
GET+POST /System/Ping, and GET /QuickConnect/Enabled (quick connect is
unsupported, so it always reports disabled).
The public info payload's Id must be stable across restarts (Jellyfin
clients cache ServerId), so it reuses the get-or-create Property pattern
already used for InsightsID in core/metrics/insights.go: fetch
consts.JellyfinServerIDKey from the Property repository, generating and
persisting a new UUID on first read. A dedicated key (rather than the
existing InsightsID) keeps the anonymous telemetry identifier from being
exposed on this unauthenticated endpoint.
