Scout invitations were stored in guild_applications with type 'invited',
forcing the scout list response to use charID as the invitation ID — a
known hack that made CancelGuildScout semantically incorrect.
Introduce a dedicated guild_invites table (migration 0012) with a serial
PK. The scout list now returns real invite IDs and actual InvitedAt
timestamps. CancelGuildScout cancels by PK. AcceptInvite and DeclineInvite
operate on guild_invites while player-applied applications remain in
guild_applications unchanged.
Introduce MailService as a convenience layer between handlers/services
and MailRepo. Provides Send, SendSystem, SendGuildInvite, and
BroadcastToGuild methods that encapsulate the boolean flag combinations.
GuildService now depends on MailService instead of MailRepo directly,
simplifying its mail-sending calls from verbose SendMail(..., false, true)
to clean SendSystem(recipientID, subject, body).
Guild mail broadcast logic moved from handleMsgMhfSendMail into
MailService.BroadcastToGuild.
Move business logic for guild disband, resign leadership, leave,
post scout, and answer scout from handlers into GuildService methods.
Handlers now delegate to the service layer and handle only protocol
concerns (packet parsing, ACK responses, cross-channel notifications).
Adds 22 new table-driven service tests and sentinel errors for typed
error handling (ErrNoEligibleLeader, ErrAlreadyInvited, etc.).
DonateRP left in handler due to Session coupling.
Extract business logic from handleMsgMhfOperateGuildMember into
GuildService.OperateMember, establishing the handler→service→repo
layering pattern. The handler is now ~20 lines of protocol glue
(type-assert, map action, call service, send ACK, notify).
GuildService owns authorization checks, repo coordination, mail
composition, and best-effort mail delivery. It accepts plain Go
types (no mhfpacket or Session imports), making it fully testable
with mock repos. Cross-channel notification stays in the handler
since it requires Session.
Adds 7 table-driven service-level tests covering accept/reject/kick,
authorization, repo errors, mail errors, and unknown actions.
