pin the android sdk explicitly and apply review fixes

- flake: pin build-tools and platform-tools to 37.0.0 instead of "latest", matching build.gradle.kts
- robolectric: run at sdk 35 (targetSdk) and re-record the golden
- manifest: allowBackup off, drop not-yet-used permissions
- theme: drop no-op status/nav bar colors (edge-to-edge)
- deps: kotlin 2.1.20, drop unused deps and test runner
- wrapper: regenerate jar from 8.11.1, add distributionSha256Sum
- remove stale README

flake.nix

@@ -24,7 +24,8 @@
           };
           android = pkgs.androidenv.composeAndroidPackages {
             platformVersions = [ "35" ];
-            buildToolsVersions = [ "latest" ];
+            buildToolsVersions = [ "37.0.0" ];
+            platformToolsVersion = "37.0.0";
             includeEmulator = false;
             includeSystemImages = false;
             includeNDK = false;