Extract all direct database calls from entranceserver (2 calls) and
API server (17 calls) into typed repository interfaces with PostgreSQL
implementations, matching the pattern established in signserver and
channelserver.
Entranceserver: EntranceServerRepo, EntranceSessionRepo
API server: APIUserRepo, APICharacterRepo, APISessionRepo
Also fix the 3 remaining fmt.Sprintf calls inside logger invocations
in handlers_commands.go and handlers_stage.go, replacing them with
structured zap fields.
Unskip 5 TestNewAuthData* tests that previously required a real
database — they now run with mock repos.
The config package used `package _config` with a leading underscore,
which is unconventional in Go. Rename to `package config` (matching the
directory name) and use `cfg` as the standard import alias across all
93 importing files.
Add package-level documentation (doc.go) to all 22 first-party
packages and godoc comments to ~150 previously undocumented
exported symbols across common/, network/, and server/.
