Replace docker with nix for reproducible build for Android

.github/workflows/android-nix.yml

@@ -0,0 +1,46 @@
+name: Android Nix Build
+
+on:
+  push:
+    branches: ["main"]
+    paths:
+      - "android/**"
+      - "shell.nix"
+      - ".github/workflows/android-nix.yml"
+  pull_request:
+    branches: ["main"]
+    paths:
+      - "android/**"
+      - "shell.nix"
+      - ".github/workflows/android-nix.yml"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Build (Nix)
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+        with:
+          submodules: recursive
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Install Rust Android targets
+        run: nix-shell shell.nix --run "rustup default stable && rustup target add x86_64-linux-android aarch64-linux-android armv7-linux-androideabi"
+
+      - name: Build debug APK
+        run: |
+          touch android/local.properties
+          nix-shell shell.nix --run "cd android && ./gradlew assembleGoogleDebug --no-configuration-cache"
+        env:
+          GPR_USERNAME: ${{ github.actor }}
+          GPR_TOKEN: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -94,7 +94,7 @@ Platform-specific commands remain available through the [`ios`](ios/justfile) an
 - Track work on the [GitHub Project Board](https://github.com/orgs/gemwalletcom/projects/2)
 - See the public [Roadmap](https://github.com/orgs/gemwalletcom/projects/4)
 
-See [CONTRIBUTING.md](CONTRIBUTING.md) for contribution guidelines and [android/reproducible/README.md](android/reproducible/README.md) for Android release verification details.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for contribution guidelines and [android/reproducible/README.md](android/reproducible/README.md) for Android reproducible build verification.
 
 ## Community
 

android/AGENTS.md

@@ -4,14 +4,14 @@ Guidance for Coding Agents working in the Android app.
 
 ## Skills
 
-Read this file first, then load the relevant skills before editing Android code. `development-commands.md`, `project-overview.md`, and `code-style.md` are the default set for most tasks. Load `setup.md` for environment/bootstrap work and `release-and-verification.md` for Docker, reproducible builds, or release packaging.
+Read this file first, then load the relevant skills before editing Android code. `development-commands.md`, `project-overview.md`, and `code-style.md` are the default set for most tasks. Load `setup.md` for environment/bootstrap work and `release-and-verification.md` for release packaging.
 
 - [Project Overview](skills/project-overview.md) — Repo structure, technologies, and build flavor layout
 - [Setup](skills/setup.md) — Prerequisites, bootstrap, and local credential requirements
 - [Development Commands](skills/development-commands.md) — Gradle and `just` workflows for build, test, generate, and lint
 - [Code Style](skills/code-style.md) — Kotlin, Compose, DI, and validation expectations
 - [Testing](skills/testing.md) — Test organization, mocks, unit and instrumented test patterns
-- [Release and Verification](skills/release-and-verification.md) — Docker, reproducible builds, artifact verification, and CI/release context
+- [Release](skills/release-and-verification.md) — Release builds and CI/release context
 - [Troubleshooting](skills/troubleshooting.md) — Common pitfalls, recovery commands, and important file locations
 
 ## Related Guides