Rename application identifier to space.rcmd.android.sizzle

Global rename of the app/package identifier from
com.reactorcoremeltdown.sizzletracker to space.rcmd.android.sizzle:

- build.gradle.kts: applicationId + namespace.
- Move the Kotlin source tree (main + test) and rewrite every package/import.
- native_audio.cpp: JNI symbol names (Java_space_rcmd_android_sizzle_...) so the
  Oboe callback still links against the relocated NativeAudioBridge.
- docs: package/file-map header.

The desktop-project GitHub URLs (github.com/reactorcoremeltdown/sizzletracker)
and the Reactorcoremeltdown copyright/SPDX author identity are intentionally left
unchanged. Note: the new applicationId installs as a separate package (existing
installs won't upgrade in place).

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

app/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 }
 
 android {
-    namespace = "com.reactorcoremeltdown.sizzletracker"
+    namespace = "space.rcmd.android.sizzle"
     compileSdk = 34
 
     // Native (Oboe) low-latency output backend; see src/main/cpp.
@@ -17,7 +17,7 @@ android {
     ndkVersion = "27.2.12479018"
 
     defaultConfig {
-        applicationId = "com.reactorcoremeltdown.sizzletracker"
+        applicationId = "space.rcmd.android.sizzle"
         // minSdk 26 (Android 8.0) is the floor for the native MIDI API
         // (android.media.midi) and AAudio low-latency audio we rely on.
         minSdk = 26