Move EnsureExists + GetAllScores + compute loop from handler into
AchievementService.GetAll, and validation + ensure + increment into
AchievementService.Increment. Handlers now delegate to the service
layer for business logic while retaining protocol response building.
GetAchData stays as a pure function in handlers_achievement.go per plan.
Leverage the new repository interfaces to test handler logic without
a database. Adds shared mock implementations (achievement, mail,
character, goocoo, guild) and 32 new handler tests covering
achievement, mail, cafe/boost, and goocoo handlers.
Port test files from v9.2.x-stable branch to increase channelserver
coverage from 13.8% to 25.6% (556 tests passing).
Adapted all files to main's struct definitions: config import alias,
Airou/CatDefinition rename, packet field mismatches, Raviente struct
differences, and maxPlayers defaults. Removed tests referencing
production code not yet on main (Player, FestivalColour, etc.).
Excluded handlers_register_test.go (Raviente completely redesigned).
