feat: turbostarter boilerplate

Production-ready Next.js boilerplate with:
- Runtime env validation (fail-fast on missing vars)
- Feature-gated config (S3, Stripe, email, OAuth)
- Docker + Coolify deployment pipeline
- PostgreSQL + pgvector, MinIO S3, Better Auth
- TypeScript strict mode (no ignoreBuildErrors)
- i18n (en/es), AI modules, billing, monitoring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.context/turbostarter-framework-context/sections/mobile/auth/oauth/google.md

@@ -0,0 +1,71 @@
+---
+title: Google
+description: Configure "Sign in with Google" for your mobile application.
+url: /docs/mobile/auth/oauth/google
+---
+
+# Google
+
+**"Sign in with Google"** enables a fast account-chooser experience on mobile (especially on Android). Configure your platform credentials, prompt the native account picker, then exchange the returned token on your backend to create a session with your auth server.
+
+<Callout title="Platform support">
+  On Android, Google Sign‑In uses [Google Identity
+  Services](https://developers.google.com/identity?hl=pl) and integrates with
+  the system account chooser. On iOS, the recommended Expo flow uses
+  [expo-auth-session](https://docs.expo.dev/versions/latest/sdk/auth-session/)
+  with Google for a native, web-based sign-in experience.
+</Callout>
+
+![Sign in with Google](/images/docs/mobile/auth/sign-in-with-google.png)
+
+## Why use Google authentication?
+
+<Cards>
+  <Card title="First-class native UX">
+    Account picker and token storage integrated with the OS for speed and familiarity.
+  </Card>
+
+  <Card title="Seamless across platforms">
+    Android native chooser; iOS polished experience via Expo.
+  </Card>
+
+  <Card title="Secure by default">
+    Tokens are verified server-side with [Better Auth](https://www.better-auth.com/docs/authentication/google) before a session is issued.
+  </Card>
+
+  <Card title="Faster onboarding">
+    Reduce friction with one-tap sign-in and fewer passwords to remember.
+  </Card>
+
+  <Card title="Scalable">
+    Built on [Google Identity Services](https://developers.google.com/identity?hl=pl) and best-practice OAuth flows.
+  </Card>
+</Cards>
+
+## Requirements
+
+* Configure [Google Cloud OAuth Client IDs](https://react-native-google-signin.github.io/docs/setting-up/get-config-file) (Android package + SHA-1, iOS bundle ID) in the [Google Cloud Console](https://console.cloud.google.com/)
+* Build with [EAS](/docs/mobile/publishing/checklist) to ensure native credentials are embedded correctly
+* Add your app deep link scheme to the auth server's [trusted origins configuration](/docs/mobile/auth/configuration)
+
+Check the [Better Auth documentation](https://www.better-auth.com/docs/authentication/google) and [`@react-native-google-signin/google-signin` documentation](https://react-native-google-signin.github.io) for steps to configure your server verification, client IDs and more.
+
+## High-level flow
+
+1. Configure Google OAuth Client IDs for Android and iOS in [Google Cloud Console](https://console.cloud.google.com/).
+2. Initialize the Google auth request in your app and render a "Sign in with Google" button.
+3. Prompt the account chooser; on success you receive an `idToken` and/or `accessToken`.
+4. Send the tokens to the API powered by [Better Auth](https://www.better-auth.com/docs/authentication/google) to verify and establish a session.
+5. Persist the session and proceed to the app.
+
+For a more in-depth overview of Google authentication, including implementation details, platform caveats, and advanced configuration, see the following resources:
+
+<Cards>
+  <Card title="Use Google Authentication" href="https://docs.expo.dev/guides/google-authentication/" description="docs.expo.dev" />
+
+  <Card title="Login with Google" href="https://www.better-auth.com/docs/authentication/google" description="better-auth.com" />
+
+  <Card title="React Native Google Sign In" href="https://react-native-google-signin.github.io/" description="react-native-google-signin.github.io" />
+
+  <Card title="Authenticate users with Sign in with Google" href="https://developer.android.com/identity/sign-in/credential-manager-siwg" description="developer.android.com" />
+</Cards>