Android: R8 shrinking, optimisation and resource shrinking for the release build

isMinifyEnabled and isShrinkResources on the release build type with
proguard-android-optimize.txt and an app proguard-rules.pro that adds no rules:
the libraries' consumer rules cover kotlinx.serialization, Room 3, Hilt, Ktor,
WorkManager (worker class names kept) and Firebase. Debug is unchanged.
Signed release APK 43 356 272 -> 11 019 453 bytes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

android/app/proguard-rules.pro

@@ -0,0 +1,3 @@
+# R8 rules for the release build of :app (SPEC §10.6). The libraries in use (kotlinx.serialization, Room 3, Hilt,
+# Ktor, OkHttp, WorkManager, Firebase messaging, Coil) ship their own consumer rules; add a rule here only for a
+# failure that was seen and with the reason beside it.