revert: remove SQLite support

An MMO server without multiplayer defeats the purpose. PostgreSQL
is the right choice and Docker Compose already solves the setup
pain. This reverts the common/db wrapper, SQLite schema, config
Driver field, modernc.org/sqlite dependency, and all repo type
changes while keeping the dashboard, wizard, and CI improvements
from the previous commit.

server/channelserver/repo_mail_test.go

@@ -1,7 +1,6 @@
 package channelserver
 
 import (
-	dbutil "erupe-ce/common/db"
 	"testing"
 
 	"github.com/jmoiron/sqlx"
@@ -14,7 +13,7 @@ func setupMailRepo(t *testing.T) (*MailRepository, *sqlx.DB, uint32, uint32) {
 	senderID := CreateTestCharacter(t, db, userID, "Sender")
 	userID2 := CreateTestUser(t, db, "mail_recipient")
 	recipientID := CreateTestCharacter(t, db, userID2, "Recipient")
-	repo := NewMailRepository(dbutil.Wrap(db))
+	repo := NewMailRepository(db)
 	t.Cleanup(func() { TeardownTestDB(t, db) })
 	return repo, db, senderID, recipientID
 }