fix(android): use a unique namespace to avoid collision with analytics-kotlin (#215)

The core plugin declared namespace 'com.segment.analytics', which is also
the manifest package of com.segment.analytics.kotlin:android. When both end
up in an app's dependency graph (e.g. via an SDK that embeds analytics-kotlin),
AGP 9 fails the build with a duplicate-namespace manifest-merger error.
Rename to com.segment.analytics.flutter and drop the deprecated manifest
package= attribute. Dart API and Kotlin source packages are unchanged.

Fixes #214

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: MarcinusX

packages/core/android/build.gradle

@@ -25,7 +25,7 @@ apply plugin: 'com.android.library'
 apply plugin: 'kotlin-android'
 
 android {
-    namespace 'com.segment.analytics'
+    namespace 'com.segment.analytics.flutter'
     compileSdkVersion 35 //Patch for for Github issue #147
 
     compileOptions {

packages/core/android/src/main/AndroidManifest.xml

@@ -1,3 +1,2 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-  package="com.segment.analytics">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
 </manifest>