Refactor to eliminate hardcoded identifiers

Read package identifier and app group ID from Info.plist at runtime
via AppConfiguration. This enables SFM.System to use TeamID-prefixed
app group format required by macOS Sequoia, fixing the privacy prompt
when accessing app group data.

SystemExtension/Info.plist

@@ -2,10 +2,14 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
+	<key>BasePackageIdentifier</key>
+	<string>$(BASE_PACKAGE_IDENTIFIER)</string>
+	<key>AppGroupIdentifier</key>
+	<string>$(APP_GROUP_IDENTIFIER)</string>
 	<key>NetworkExtension</key>
 	<dict>
 		<key>NEMachServiceName</key>
-		<string>group.io.nekohasekai.sfavt.system</string>
+		<string>$(APP_GROUP_IDENTIFIER).system</string>
 		<key>NEProviderClasses</key>
 		<dict>
 			<key>com.apple.networkextension.packet-tunnel</key>

SystemExtension/SystemExtension.entitlements

@@ -10,7 +10,7 @@
 	</array>
 	<key>com.apple.security.application-groups</key>
 	<array>
-		<string>group.io.nekohasekai.sfavt</string>
+		<string>$(TeamIdentifierPrefix)$(BASE_PACKAGE_IDENTIFIER)</string>
 	</array>
 	<key>com.apple.security.app-sandbox</key>
 	<false/>