feat(web): visual rule builder with geo, CIDR and wildcard pickers

The rule editor no longer requires writing expr by hand. Conditions are rows of
field + operator + values joined with AND or OR, each row negatable, and the
generated expression is shown live and validated by the engine before a rule is
accepted. Raw expression and YAML editing are still available.

Fields cover the connection (protocol, source/destination IP and port), domains
(TLS SNI, QUIC SNI, DNS query name), HTTP (host, path, method, User-Agent) and
protocol detection. Operators cover CIDR membership, GeoIP countries, GeoSite
categories, port ranges, wildcards, substrings and regular expressions.
Multiple values in a row are OR-ed, so one row holds a whole domain or country
list.

Wildcards compile to the cheapest expression that matches them: *.x.com
becomes endsWith, x.* startsWith, *ad* contains, and only a star in the
middle falls back to a regular expression. Values are validated as they are
typed, including a hint when a star is used with an operator that would match
it literally.

Country and category pickers are backed by the databases the engine actually
loaded, via a new GET /api/v1/geo endpoint (cached, loaded on demand) built on
new listing methods in the geo package. Country names and flags come from
Intl.DisplayNames, so no name table is shipped. Note that the v2geo format has
no AS numbers; the provider groups it does contain (cloudflare, google,
telegram, ...) are listed alongside the countries.

Opening an existing rule parses its expression back into conditions. Anything
the builder cannot represent opens in the expression editor with a warning
rather than being rewritten. ruleset/expr_test.go pins the canonical
expressions the builder generates and compiles them with the real engine, and
the devserver now uses the real ruleset compiler so the same errors show up
during frontend work.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.zh.md

@@ -36,6 +36,10 @@ Telegram 群组： https://t.me/OpGFW
 OpenGFW 内置了一个可选的 Web 控制面板：实时流量统计、带解析器属性的实时事件流，以及可以校验并热加载规则的规则编辑器。
 界面同时适配手机和桌面浏览器。
 
+规则既可以用条件列表来写——选择字段（SNI、DNS 域名、HTTP Host、IP、端口、识别到的协议）、
+条件（通配符、CIDR、GeoIP 国家/地区、GeoSite 分类、端口区间、正则）以及一个或多个值——
+也可以直接编写 expr 表达式或 YAML。国家/地区与站点分类直接从引擎加载的 geo 数据库中选择。
+
 在配置文件中启用：
 
 ```yaml