feat(email): 初始化自建邮箱 MVP

- 新增 Go + SQLite 后端，支持登录、域名、邮箱、别名、联系人、规则、统计与邮件收发。
- 新增 Webmail 前端，支持多邮箱切换、邮件列表/阅读/写信、附件、搜索、主题切换与个人中心。
- 新增 Docker Compose 部署骨架，补充 Postfix、Dovecot、OpenDKIM、Nginx 配置与部署说明。

deploy/dovecot/Dockerfile

@@ -0,0 +1,10 @@
+FROM debian:bookworm-slim
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends dovecot-core dovecot-imapd dovecot-lmtpd dovecot-sqlite ssl-cert ca-certificates && rm -rf /var/lib/apt/lists/*
+COPY dovecot.conf /etc/dovecot/dovecot.conf
+COPY dovecot-sql.conf.ext /etc/dovecot/dovecot-sql.conf.ext
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+EXPOSE 993 24 12345
+CMD ["/entrypoint.sh"]
+

deploy/dovecot/dovecot-sql.conf.ext

@@ -0,0 +1,5 @@
+driver = sqlite
+connect = /data/lanqin.db
+default_pass_scheme = BLF-CRYPT
+password_query = SELECT address AS user, password_hash AS password FROM mailboxes WHERE address = '%u' AND status = 'active'
+user_query = SELECT '/var/mail/vhosts/' || substr(address, instr(address, '@') + 1) || '/' || local_part AS home, 'maildir:/var/mail/vhosts/' || substr(address, instr(address, '@') + 1) || '/' || local_part || '/Maildir' AS mail, 5000 AS uid, 5000 AS gid FROM mailboxes WHERE address = '%u' AND status = 'active'

deploy/dovecot/dovecot.conf

@@ -0,0 +1,48 @@
+protocols = imap lmtp
+listen = *
+base_dir = /var/run/dovecot/
+
+log_path = /dev/stderr
+info_log_path = /dev/stdout
+
+ssl = yes
+ssl_cert = </etc/ssl/certs/ssl-cert-snakeoil.pem
+ssl_key = </etc/ssl/private/ssl-cert-snakeoil.key
+
+mail_home = /var/mail/vhosts/%d/%n
+namespace inbox {
+  inbox = yes
+  mailbox Drafts { special_use = \Drafts }
+  mailbox Sent { special_use = \Sent }
+  mailbox Trash { special_use = \Trash }
+  mailbox Archive { special_use = \Archive }
+  mailbox Spam { special_use = \Junk }
+}
+
+passdb {
+  driver = sql
+  args = /etc/dovecot/dovecot-sql.conf.ext
+}
+userdb {
+  driver = sql
+  args = /etc/dovecot/dovecot-sql.conf.ext
+}
+
+service imap-login {
+  inet_listener imaps { port = 993 ssl = yes }
+}
+
+service lmtp {
+  inet_listener lmtp { address = 0.0.0.0 port = 24 }
+}
+
+service auth {
+  inet_listener postfix-auth {
+    address = 0.0.0.0
+    port = 12345
+  }
+}
+
+protocol lmtp {
+  postmaster_address = postmaster@localhost
+}

deploy/dovecot/entrypoint.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+set -eu
+addgroup --system --gid 5000 vmail 2>/dev/null || true
+adduser --system --uid 5000 --gid 5000 --home /var/mail/vhosts --no-create-home vmail 2>/dev/null || true
+mkdir -p /var/mail/vhosts
+chown -R 5000:5000 /var/mail/vhosts
+exec dovecot -F