docs: refresh README

Clarify what this repo is, consolidate install paths (releases, site,
Zapstore badge), and trim product-only sections.

README.md

@@ -1,33 +1,53 @@
 # Zapstore
 
-The open app store powered by your social network
+[![Release](https://img.shields.io/github/v/release/zapstore/zapstore)](https://github.com/zapstore/zapstore/releases)
+[![License: MIT](https://img.shields.io/github/license/zapstore/zapstore)](LICENSE.md)
+[![Flutter](https://img.shields.io/badge/Flutter-3.38.6-02569B?logo=flutter)](https://flutter.dev)
 
-[https://zapstore.dev](https://zapstore.dev)
+**Open Android app store: discover, install, and update apps published directly by developers.**
+
+This repo is the [Flutter](https://flutter.dev) mobile app for [Zapstore](https://zapstore.dev). Listings and publisher identity sync from Nostr relays; APKs are verified (file hash and signing certificate) before install.
+
+## Get the app
+
+[GitHub Releases](https://github.com/zapstore/zapstore/releases) (APK) · [zapstore.dev](https://zapstore.dev) · install from Zapstore (badge below)
+
+<p align="center">
+  <a href="https://zapstore.dev/apps/naddr1qvzqqqr7pvpzq7xwd748yfjrsu5yuerm56fcn9tntmyv04w95etn0e23xrczvvraqqgxgetk9eaxzurnw3hhyefwv9c8qakg5jt">
+    <img src="./assets/images/badge.png" alt="Get it on Zapstore" width="200">
+  </a>
+</p>
+
+<p align="center">
+  <img src="./fastlane/metadata/android/images/zapstore_screenshots/zapstore_screenshot.png" alt="Zapstore app screenshot" width="280">
+</p>
 
 ## Build from source
 
+Flutter **3.38.6** (see [`.fvmrc`](.fvmrc); [FVM](https://fvm.app) optional). Android SDK required for APK builds.
+
 ```bash
 flutter pub get
 flutter build apk --split-per-abi --debug
 ```
 
-APK will be available at `build/app/outputs/flutter-apk`.
+Output: `build/app/outputs/flutter-apk/`
 
-<a href="https://zapstore.dev/apps/naddr1qvzqqqr7pvpzq7xwd748yfjrsu5yuerm56fcn9tntmyv04w95etn0e23xrczvvraqqgxgetk9eaxzurnw3hhyefwv9c8qakg5jt">
+```bash
-  <img src="./assets/images/badge.png"
+flutter analyze && flutter test
-  alt="Get it on Zapstore" width="200">
+```
-</a>
+
+## Docs in this repo
+
+- [Changelog](CHANGELOG.md)
+- [Architecture & guidelines](spec/guidelines/) (for contributors and agents)
 
 ## Contributing
 
-Unless it's a minor fix, please reach out to us first before working on any contribution!
+Minor fixes: PRs welcome. For larger changes, please reach out first while the project is in beta.
 
-We will have a clearer process to contribute once we are out of beta.
+Tested with [BrowserStack](https://www.browserstack.com/).
-
-## Testing
-
-This project is tested with [BrowserStack](https://www.browserstack.com/).
 
 ## License
 
-MIT
+[MIT](LICENSE.md)