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/app/build.gradle.kts

@@ -27,6 +27,11 @@ android {
     namespace = "com.dtourolle.jellytau"
     defaultConfig {
         manifestPlaceholders["usesCleartextTraffic"] = "false"
+        // Launcher/app names come from placeholders so the debug build can
+        // rename itself without touching the generated strings.xml (a
+        // resValue() override there would collide with Tauri's own entries).
+        manifestPlaceholders["appLabel"] = "@string/app_name"
+        manifestPlaceholders["activityLabel"] = "@string/main_activity_title"
         applicationId = "com.dtourolle.jellytau"
         minSdk = 24
         targetSdk = 36
@@ -45,6 +50,21 @@ android {
     }
     buildTypes {
         getByName("debug") {
+            // Distinct applicationId so the debug build installs SIDE BY SIDE
+            // with a release/store install instead of demanding an uninstall
+            // (different signing keys on the same package = INSTALL_FAILED_
+            // UPDATE_INCOMPATIBLE). It gets its own data dir, its own settings
+            // and its own offline cache — the two are fully independent apps.
+            //
+            // This changes only the *application* id. The Kotlin/JNI classes
+            // stay in the `namespace` package (com.dtourolle.jellytau), so the
+            // fully-qualified class names Rust looks up over JNI, the manifest
+            // <service> entry and the R8 keep rules are all unaffected. The
+            // FileProvider authority is already ${applicationId}-relative.
+            applicationIdSuffix = ".debug"
+            versionNameSuffix = "-debug"
+            manifestPlaceholders["appLabel"] = "JellyTau Debug"
+            manifestPlaceholders["activityLabel"] = "JellyTau Debug"
             manifestPlaceholders["usesCleartextTraffic"] = "true"
             isDebuggable = true
             isJniDebuggable = true