android: add BAL Reader app (Chaquopy codec bridge) + frame progress bar

First commit of the Android 'BAL Reader' app: a camera scanner that decodes
the same four transfer formats the plugin exports (BAL QR v2/legacy, BC-UR
v1/v2, BBQR) by running the synced bal/core codecs verbatim under Chaquopy
plus a verify_chain regression. Adds android/scripts/build_apk.py (resync
codecs, gradle build, prints APK sha256) and sync_codecs.py.

UI: during capture a thin mint fill-bar above the camera preview shows
received/total frames (FrameProgressBar), complementing the exact n/N label.

android/settings.gradle.kts

@@ -0,0 +1,23 @@
+pluginManagement {
+    repositories {
+        google {
+            content {
+                includeGroupByRegex("com\\.android.*")
+                includeGroupByRegex("com\\.google.*")
+                includeGroupByRegex("androidx.*")
+            }
+        }
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.name = "BALReader"
+include(":app")