chore: 更新 .gitignore 忽略临时文件

添加忽略规则：
- Maven flattened pom 文件
- Claude Code memory 目录
- 应用日志目录
- 临时 SQL 脚本

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -83,3 +83,15 @@ node-compile-cache/
 # Frontend build artifacts
 apps/**/dist/
 packages/**/dist/
+
+# Maven flattened pom
+.flattened-pom.xml
+
+# Claude Code memory
+.claude/
+
+# Application logs
+logs/
+
+# SQL scripts (temporary)
+update_tenant.sql