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/api/repo_event.go

@@ -6,15 +6,15 @@ import (
 	"errors"
 	"time"
 
-	dbutil "erupe-ce/common/db"
+	"github.com/jmoiron/sqlx"
 )
 
 type apiEventRepository struct {
-	db *dbutil.DB
+	db *sqlx.DB
 }
 
 // NewAPIEventRepository creates an APIEventRepo backed by PostgreSQL.
-func NewAPIEventRepository(db *dbutil.DB) APIEventRepo {
+func NewAPIEventRepository(db *sqlx.DB) APIEventRepo {
 	return &apiEventRepository{db: db}
 }