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/extension/customization/add-package.md

@@ -0,0 +1,100 @@
+---
+title: Adding packages
+description: Learn how to add packages to your Turborepo workspace.
+url: /docs/extension/customization/add-package
+---
+
+# Adding packages
+
+<Callout title="Advanced topic" type="warn">
+  This is an **advanced topic** - you should only follow these instructions if you are sure you want to add a new package to your TurboStarter application instead of adding a folder to your application in `apps/web` or modify existing packages under `packages`. You don't need to do this to add a new page or component to your application.
+</Callout>
+
+To add a new package to your TurboStarter application, you need to follow these steps:
+
+<Steps>
+  <Step>
+    ## Generate a new package
+
+    First, enter the command below to create a new package in your TurboStarter application:
+
+    ```bash
+    turbo gen package
+    ```
+
+    Turborepo will ask you to enter the name of the package you want to create. Enter the name of the package you want to create and press enter.
+
+    If you don't want to add dependencies to your package, you can skip this step by pressing enter.
+
+    The command will have generated a new package under packages named `@turbostarter/<package-name>`. If you named it `example`, the package will be named `@turbostarter/example`.
+  </Step>
+
+  <Step>
+    ## Export a module from your package
+
+    By default, the package exports a single module using the `index.ts` file. You can add more exports by creating new files in the package directory and exporting them from the `index.ts` file or creating export files in the package directory and adding them to the `exports` field in the `package.json` file.
+
+    ### From `index.ts` file
+
+    The easiest way to export a module from a package is to create a new file in the package directory and export it from the `index.ts` file.
+
+    ```ts title="packages/example/src/module.ts"
+    export function example() {
+      return "example";
+    }
+    ```
+
+    Then, export the module from the `index.ts` file.
+
+    ```ts title="packages/example/src/index.ts"
+    export * from "./module";
+    ```
+
+    ### From `exports` field in `package.json`
+
+    **This can be very useful for tree-shaking.** Assuming you have a file named `module.ts` in the package directory, you can export it by adding it to the `exports` field in the `package.json` file.
+
+    ```json title="packages/example/package.json"
+    {
+      "exports": {
+        ".": "./src/index.ts",
+        "./module": "./src/module.ts"
+      }
+    }
+    ```
+
+    **When to do this?**
+
+    1. when exporting two modules that don't share dependencies to ensure better tree-shaking. For example, if your exports contains both client and server modules.
+    2. for better organization of your package
+
+    For example, create two exports `client` and `server` in the package directory and add them to the `exports` field in the `package.json` file.
+
+    ```json title="packages/example/package.json"
+    {
+      "exports": {
+        ".": "./src/index.ts",
+        "./client": "./src/client.ts",
+        "./server": "./src/server.ts"
+      }
+    }
+    ```
+
+    1. The `client` module can be imported using `import { client } from '@turbostarter/example/client'`
+    2. The `server` module can be imported using `import { server } from '@turbostarter/example/server'`
+  </Step>
+
+  <Step>
+    ## Use the package in your extension
+
+    You can now use the package in your extension by importing it using the package name:
+
+    ```ts title="app/popup/index.tsx"
+    import { example } from "@turbostarter/example";
+
+    console.log(example());
+    ```
+  </Step>
+</Steps>
+
+Et voilà! You have successfully added a new package to your TurboStarter extension. 🎉