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>

docs/DEVELOPER_HANDOVER.md

@@ -84,7 +84,7 @@ Three ideas hold it together:
 ## 4. Package/file map
 
 ```
-com.reactorcoremeltdown.sizzletracker
+space.rcmd.android.sizzle
 ├── SizzleApp.kt            Application = tiny DI container (Project, InputRouter, AudioEngine)
 ├── MainActivity.kt         Hosts Compose UI; forwards HW key/motion events; starts MIDI + service
 │