docs: update README to document devshell and Gitea CI/CD release workflow

README.md

@@ -2,20 +2,53 @@
 <img width="1200" height="475" alt="GHBanner" src="https://ai.google.dev/static/site-assets/images/share-ais-513315318.png" />
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-# Run and deploy your AI Studio app
+# Munich Departures
 
-This contains everything you need to run your app locally.
+An Android application for Munich public transport departures, featuring devshell and automated Gitea CI/CD workflows.
 
 View your app in AI Studio: https://ai.studio/apps/9c59cfb4-12a7-42ef-ae43-53c4408c63ad
 
-## Run Locally
+## Development Environment (Nix / Devbox)
 
-**Prerequisites:**  [Android Studio](https://developer.android.com/studio)
+This project contains a Nix development shell setup (`flake.nix` & `devbox.json`) providing consistent tooling (JDK 17 and Android SDK Platform 36 / Build-tools 36.0.0).
 
+### Entering the Devshell
+If you have [direnv](https://direnv.net/) installed, it will automatically load when you enter this directory. Alternatively, you can use:
+```bash
+nix develop
+# or
+devbox shell
+```
 
-1. Open Android Studio
-2. Select **Open** and choose the directory containing this project
-3. Allow Android Studio to fix any incompatibilities as it imports the project.
-4. Create a file named `.env` in the project directory and set `GEMINI_API_KEY` in that file to your Gemini API key (see `.env.example` for an example)
-5. Remove this line from the app's `build.gradle.kts` file: `signingConfig = signingConfigs.getByName("debugConfig")`
-6. Run the app on an emulator or physical device
+### Build Commands
+All Gradle commands should be run within the devshell environment:
+- `nix develop -c ./gradlew build` - Build the entire project
+- `nix develop -c ./gradlew assembleDebug` - Build debug APK
+- `nix develop -c ./gradlew assembleRelease` - Build release APK
+- `nix develop -c ./gradlew test` - Run all unit tests
+
+## Local Setup
+1. **Prerequisites**: [Android Studio](https://developer.android.com/studio) or the Nix development shell.
+2. Create a file named `.env` in the project root directory and set your Gemini API key (see `.env.example` for details):
+   ```env
+   GEMINI_API_KEY=your_gemini_api_key_here
+   ```
+3. Run the app on an emulator or physical device.
+
+## Gitea CI/CD & Releases
+The project features an automated Gitea release workflow configured in `.gitea/workflows/release.yml`.
+
+### Creating a Release
+To publish a new version:
+1. Bump the `versionName` in `app/build.gradle.kts` (e.g. `versionName = "0.1.0"`) and increment the `versionCode`.
+2. Commit the bump and push it:
+   ```bash
+   git commit -am "chore(release): bump version to 0.1.0"
+   git push origin main
+   ```
+3. Create and push a tag matching `v*`:
+   ```bash
+   git tag v0.1.0
+   git push origin v0.1.0
+   ```
+4. The Gitea Actions runner will detect the tag, build the release variant of the APK, rename it to `munich-departures-v0.1.0.apk`, and upload it directly to Gitea Releases.