build(android): install the debug build alongside release as its own app

Testing a debug build meant uninstalling the real one first: same
applicationId signed with a different key is INSTALL_FAILED_UPDATE_
INCOMPATIBLE, so every experiment cost the app's settings, credentials
and offline cache.

The debug build type now carries applicationIdSuffix ".debug" and
versionNameSuffix "-debug", so it installs as com.dtourolle.jellytau.debug
("JellyTau Debug", 0.5.5-debug) with its own data directory — two
independent apps on one device.

Only the *application* id is suffixed. Kotlin classes stay in the
`namespace` package com.dtourolle.jellytau, so the JNI loadClass lookups
in player/android/mod.rs, the manifest <service> entry and the R8 keep
rules are untouched, and the FileProvider authority was already
${applicationId}-relative. Launcher names come from the appLabel /
activityLabel manifestPlaceholders rather than resValue, which would
collide with Tauri's generated strings.xml; release resolves them back to
@string/app_name and merges byte-identical.

deploy-android.sh reports the target package and explains an
UPDATE_INCOMPATIBLE failure instead of leaving it raw; logcat.sh takes a
debug|release argument (it was filtering on com.jellytau.app, a package
that has never existed) and attaches by pid when the app is running.

Verified: aapt2 badging on the built APK reports
com.dtourolle.jellytau.debug / 0.5.5-debug / "JellyTau Debug", and the
release manifest merge is unchanged.

src-tauri/android/src/main/AndroidManifest.xml

@@ -11,6 +11,12 @@
   (An earlier version of this file was a partial <application> fragment on the
   assumption that Tauri merged it. It did not: the hardwareAccelerated flag it
   declared never reached any built APK. It is folded in properly below.)
+
+  ${appLabel} / ${activityLabel} are manifestPlaceholders set in
+  app/build.gradle.kts: they resolve to @string/app_name and
+  @string/main_activity_title for release, and to "JellyTau Debug" for the
+  debug build type (which also carries applicationIdSuffix ".debug" so it
+  installs alongside a release build).
 -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <uses-permission android:name="android.permission.INTERNET" />
@@ -26,7 +32,7 @@
 
     <application
         android:icon="@mipmap/ic_launcher"
-        android:label="@string/app_name"
+        android:label="${appLabel}"
         android:theme="@style/Theme.jellytau"
         android:hardwareAccelerated="true"
         android:networkSecurityConfig="@xml/network_security_config"
@@ -34,7 +40,7 @@
         <activity
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|smallestScreenSize|screenLayout|uiMode|density"
             android:launchMode="singleTask"
-            android:label="@string/main_activity_title"
+            android:label="${activityLabel}"
             android:name=".MainActivity"
             android:exported="true"
             android:supportsPictureInPicture="true"