refactor: replace raw SQL with repository interfaces in entranceserver and API server

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.

server/entranceserver/repo_interfaces.go

@@ -0,0 +1,19 @@
+package entranceserver
+
+// Repository interfaces decouple entrance server business logic from concrete
+// PostgreSQL implementations, enabling mock/stub injection for unit tests.
+
+// EntranceServerRepo defines the contract for server-related data access
+// used by the entrance server when building server list responses.
+type EntranceServerRepo interface {
+	// GetCurrentPlayers returns the current player count for a given server ID.
+	GetCurrentPlayers(serverID int) (uint16, error)
+}
+
+// EntranceSessionRepo defines the contract for session-related data access
+// used by the entrance server when resolving user locations.
+type EntranceSessionRepo interface {
+	// GetServerIDForCharacter returns the server ID where the given character
+	// is currently signed in, or 0 if not found.
+	GetServerIDForCharacter(charID uint32) (uint16, error)
+}