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/apple.md

@@ -0,0 +1,74 @@
+---
+title: Apple
+description: Configure "Sign in with Apple" for your mobile application.
+url: /docs/mobile/auth/oauth/apple
+---
+
+# Apple
+
+**"Sign in with Apple"** provides a native, privacy-preserving SSO experience on iOS. Use the system Apple button and the Apple Authentication APIs to sign users in, then verify the identity token on your backend and create a session with your auth server.
+
+<Callout title="Apple ID authentication is available on iOS only">
+  Native Apple ID authentication is available on iOS only. You are advised to
+  present the official system button (or our custom component - also compliant!)
+  and follow [Apple's Human Interface
+  Guidelines](https://developer.apple.com/design/human-interface-guidelines/sign-in-with-apple)
+  for best practices.
+</Callout>
+
+![Sign in with Apple](/images/docs/mobile/auth/sign-in-with-apple.png)
+
+## Why use native Apple ID authentication?
+
+<Cards>
+  <Card title="First-class native UX">
+    System sheet + official button, aligned with [Apple's Human Interface Guidelines](https://developer.apple.com/design/human-interface-guidelines/sign-in-with-apple) for trust and conversion.
+  </Card>
+
+  <Card title="Privacy-forward">
+    Private relay email and limited data by design, ensuring your users' privacy is protected and compliant with App Store guidelines.
+  </Card>
+
+  <Card title="Fewer passwords">
+    Fast, low-friction sign-in on iOS enabling your users to sign in without the need to remember or create additional passwords.
+  </Card>
+
+  <Card title="Secure by default">
+    JWT verification on the server with [Better Auth](https://www.better-auth.com/docs/authentication/apple), keeping your users' credentials secure.
+  </Card>
+
+  <Card title="Seamless sessions">
+    We exchange Apple credentials for an app session and persist it in the app.
+  </Card>
+</Cards>
+
+## Requirements
+
+* Enable the "Sign in with Apple" capability for your bundle identifier in the [Apple Developer Portal](https://developer.apple.com/account/resources/identifiers/list)
+* Add the entitlement and build with [EAS](/docs/mobile/publishing/checklist) (or configure natively)
+* Ensure your app's deep link scheme is added to the auth server's [trusted origins configuration](/docs/mobile/auth/configuration)
+
+Check the [Better Auth documentation](https://www.better-auth.com/docs/authentication/apple) for more details on how to configure all the required keys and certificates.
+
+## High-level flow
+
+1. Check availability with `AppleAuthentication.isAvailableAsync()`.
+2. Render the system `AppleAuthenticationButton` or custom TurboStarter component.
+3. Call `AppleAuthentication.signInAsync()` requesting `FULL_NAME` and/or `EMAIL` as needed.
+4. Send the returned `idTokeb` identifier to the API powered by [Better Auth](https://www.better-auth.com/docs/authentication/apple) to verify and establish a session.
+5. Optionally track credential state with `AppleAuthentication.getCredentialStateAsync(user)`.
+
+<Callout type="warn" title="Verify on the server">
+  Always verify the JWT signature from `idToken` on your backend using Apple's
+  public keys before creating a session.
+</Callout>
+
+For a more in-depth overview of Apple ID authentication—including implementation details, platform caveats, and advanced configuration—see the following resources:
+
+<Cards>
+  <Card title="Expo AppleAuthentication" href="https://docs.expo.dev/versions/latest/sdk/apple-authentication/" description="docs.expo.dev" />
+
+  <Card title="Login with Apple" href="https://www.better-auth.com/docs/authentication/apple" description="better-auth.com" />
+
+  <Card title="Sign in with Apple" href="https://developer.apple.com/documentation/sign_in_with_apple" description="developer.apple.com" />
+</Cards>