Feature: extended filter rules — attachment field + multi-value conditions

Adds an "Attachment" condition field (is present / of type <ext>) backed by
the RFC 5703 Sieve mime extension, matching the filename in both
Content-Disposition and Content-Type headers so real-world senders that only
put the name in Content-Type (Microsoft SMTPSVC, etc.) are caught. Users type
extensions (pdf, doc) not MIME types.

Also makes each text condition accept comma-separated multiple values emitted
as a Sieve string list (OR within the condition), so "(domain1 OR domain2)
AND attachment pdf/xml" is expressible in one rule. value is now string |
string[] (single-value rules stay strings -> backward compatible). New filter
locale keys in all 17 locales.

locales/zh/common.json

@@ -1632,7 +1632,10 @@
       "actions": "操作",
       "add_action": "添加操作",
       "stop_processing": "停止处理后续规则",
+      "attachment_type_placeholder": "例如：pdf、doc、jpg",
+      "value_placeholder_multi": "值（多个用逗号分隔）",
       "condition_fields": {
+        "attachment": "附件",
         "from": "发件人",
         "to": "收件人",
         "cc": "抄送",
@@ -1642,6 +1645,8 @@
         "body": "正文"
       },
       "comparators": {
+        "has_any": "存在",
+        "has_type": "类型为",
         "contains": "包含",
         "not_contains": "不包含",
         "is": "等于",