支持邮箱 + 别名自动回溯主账号

[ZeroPointSix]

Summary

• mailbox_resolver 新增 normalize_alias_email，统一将 user+tag@domain 规范化为主地址，resolve_mailbox 默认走该规范化逻辑。
• controllers/emails.py 在 external common 参数解析与内部邮件读取入口接入别名规范化，保证主地址与别名地址读取行为一致。
• 补齐别名能力测试与迁移兼容测试（normalize、flow、migration_compat、resolver 别名回溯），并更新 CHANGELOG 与 WORKSPACE 记录。

Test

• python -m unittest tests.test_email_alias_normalize tests.test_mailbox_resolver tests.test_email_alias_flow tests.test_email_alias_migration_compat -v
• 结果：Ran 20 tests in 7.103s, OK

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud