speaker: make AudioRoute a real Capacitor plugin PACKAGE so it registers (device log: has:0)

Device telemetry proved the app-embedded AudioRoute class never registered (not in
Capacitor.Plugins) — appending a CAPBridgedPlugin to AppDelegate.swift gets stripped/undiscovered
in release builds. The plugins that DO register (Share, Camera, Filesystem) are all npm packages
wired by cap sync. So AudioRoute is now a local plugin package (mobile/plugins/audio-route,
file: dep in mobile/package.json) with a podspec + CAPBridgedPlugin Swift — cap sync adds its pod
and Capacitor registers it like the others. load() sets the launch speaker default; setSpeaker({on})
overrides the output port. inject-audio.js no longer injects the plugin class (would duplicate);
it keeps only the AppDelegate launch default as a fallback.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

mobile/plugins/audio-route/AudioRoutePlugin.podspec

@@ -0,0 +1,17 @@
+require 'json'
+
+package = JSON.parse(File.read(File.join(__dir__, 'package.json')))
+
+Pod::Spec.new do |s|
+  s.name = 'AudioRoutePlugin'
+  s.version = package['version']
+  s.summary = package['description']
+  s.license = package['license']
+  s.homepage = 'https://bizgaze.com'
+  s.author = 'BizGaze'
+  s.source = { :git => 'https://bizgaze.com/audio-route.git', :tag => s.version.to_s }
+  s.source_files = 'ios/Sources/**/*.{swift,h,m}'
+  s.ios.deployment_target = '14.0'
+  s.dependency 'Capacitor'
+  s.swift_version = '5.1'
+end