feat(event): 접속 국가별 이벤트 언어 필터를 적용한다

docs/20260819_이벤트_접속국가별_언어필터/20260819_event_lang_ddl.sql

@@ -0,0 +1,41 @@
+SET @schema_name := DATABASE();
+
+SET @lang_column_exists := (
+    SELECT COUNT(1)
+    FROM information_schema.columns
+    WHERE table_schema = @schema_name
+      AND table_name = 'event'
+      AND column_name = 'lang'
+);
+
+SET @add_lang_column_sql := IF(
+    @lang_column_exists = 0,
+    'ALTER TABLE `event` ADD COLUMN lang VARCHAR(10) NULL COMMENT ''이벤트 노출 언어'' AFTER title',
+    'SELECT ''event.lang already exists'' AS message'
+);
+
+PREPARE add_lang_column_stmt FROM @add_lang_column_sql;
+EXECUTE add_lang_column_stmt;
+DEALLOCATE PREPARE add_lang_column_stmt;
+
+UPDATE `event`
+SET lang = 'KO'
+WHERE lang IS NULL;
+
+SET @lang_column_nullable := (
+    SELECT IS_NULLABLE
+    FROM information_schema.columns
+    WHERE table_schema = @schema_name
+      AND table_name = 'event'
+      AND column_name = 'lang'
+);
+
+SET @alter_lang_column_sql := IF(
+    @lang_column_nullable = 'YES',
+    'ALTER TABLE `event` MODIFY COLUMN lang VARCHAR(10) NOT NULL DEFAULT ''KO'' COMMENT ''이벤트 노출 언어 (KO 기본, EN/JA 등록 가능)''',
+    'SELECT ''event.lang already normalized'' AS message'
+);
+
+PREPARE alter_lang_column_stmt FROM @alter_lang_column_sql;
+EXECUTE alter_lang_column_stmt;
+DEALLOCATE PREPARE alter_lang_column_stmt;