Align the China region to the official cn profile

The region value is cn, the China files live under default/regions/cn/, and
omarchy-apply-pacman renders pacman for every caller: the .cn twins of the
channel servers first, then .org, USTC and ArchLinuxCN. Switching to China
installs and trusts the ArchLinuxCN keyring. A migration renames china to cn
and repoints the drop-in links.

default/regions/cn/cargo.toml

@@ -0,0 +1,5 @@
+[source.crates-io]
+replace-with = "aliyun"
+
+[source.aliyun]
+registry = "sparse+https://mirrors.aliyun.com/crates.io-index/"

default/regions/cn/environment.conf

@@ -0,0 +1,8 @@
+NPM_CONFIG_REGISTRY=https://registry.npmmirror.com
+PIP_INDEX_URL=https://mirrors.aliyun.com/pypi/simple/
+UV_DEFAULT_INDEX=https://mirrors.aliyun.com/pypi/simple/
+GOPROXY=https://mirrors.aliyun.com/goproxy/,direct
+RUSTUP_DIST_SERVER=https://mirrors.aliyun.com/rustup
+RUSTUP_UPDATE_ROOT=https://mirrors.aliyun.com/rustup/rustup
+BUNDLE_MIRROR__ALL=https://mirrors.aliyun.com/rubygems/
+MAVEN_ARGS=--global-settings /usr/share/omarchy/default/regions/cn/maven-settings.xml

default/regions/cn/gemrc

@@ -0,0 +1,3 @@
+---
+:sources:
+- https://mirrors.aliyun.com/rubygems/

default/regions/cn/maven-settings.xml

@@ -0,0 +1,9 @@
+<settings>
+  <mirrors>
+    <mirror>
+      <id>aliyun</id>
+      <mirrorOf>central</mirrorOf>
+      <url>https://maven.aliyun.com/repository/public</url>
+    </mirror>
+  </mirrors>
+</settings>

default/regions/cn/pacman/servers.sed

@@ -0,0 +1 @@
+s|^Server = https://\([a-z-]*\)\.omarchy\.org/\(.*\)$|Server = https://\1.omarchy.cn/\2\n&|