start kotlin/jetpack compose rewrite

replace the flutter project with a gradle/compose android app:
- nix flake dev shell (jdk21, android sdk 35, build-tools 37, gradle)
- material3 app with a placeholder screen
- roborazzi/robolectric screenshot tests with one golden
- carry over the existing launcher/notification assets

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1780453794,
+        "narHash": "sha256-bXMRa9VTsHSPXL4Cw8R6JJLQeY3Y/IP4+YJCYVmQ7FY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6b316287bae2ee04c9b93c8c858d930fd07d7338",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6b316287bae2ee04c9b93c8c858d930fd07d7338",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}