refactor/ migrate from OpenAI to OpenRouter integration

Major improvements to AI integration and developer experience:

## OpenRouter Migration
- Replaced @ai-sdk/openai with @openrouter/ai-sdk-provider
- Updated chat API route to use OpenRouter for access to 100+ AI models
- Changed environment variables from OPENAI_* to OPENROUTER_*
- Updated default model from gpt-5-mini to openai/gpt-5-mini
- Benefits: Users can now access multiple AI providers (OpenAI, Anthropic, etc.) through a single unified API

## Documentation Overhaul
- Expanded CLAUDE.md from 3 lines to comprehensive 225-line guide
- Added complete project structure, tech stack overview, and AI integration guidelines
- Documented all environment variables, scripts, and common tasks
- Added critical rules for AI assistants working with the codebase
- Enhanced checkpoint command with detailed step-by-step instructions

## README Updates
- Updated feature list to highlight OpenRouter integration
- Revised setup instructions for OpenRouter API key acquisition
- Updated environment variable examples and deployment configuration
- Changed all OpenAI references to OpenRouter throughout documentation

## Create Command Updates
- Bumped create-agentic-app version from 1.0.0 to 1.0.1
- Synchronized all template files with main project documentation
- Updated template env.example and package.json with OpenRouter configuration

## Dependency Updates
- Added @openrouter/ai-sdk-provider@^1.2.0
- Updated @ai-sdk/openai from ^2.0.53 to ^2.0.60
- Updated @ai-sdk/react from ^2.0.78 to ^2.0.86
- Updated ai from ^5.0.78 to ^5.0.86
- Updated better-auth from ^1.3.29 to ^1.3.34
- Updated drizzle-kit from ^0.31.5 to ^0.31.6
- Updated eslint from ^9.38.0 to ^9.39.0
- Various type definition updates

Breaking Changes:
- Projects must update environment variables from OPENAI_* to OPENROUTER_*
- API keys must be obtained from openrouter.ai instead of platform.openai.com
- Model names now follow OpenRouter format (e.g., "openai/gpt-5-mini")

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

README.md

@@ -6,7 +6,7 @@ A complete agentic coding boilerplate with authentication, PostgreSQL database,
 
 - **🔐 Authentication**: Better Auth with Google OAuth integration
 - **🗃️ Database**: Drizzle ORM with PostgreSQL
-- **🤖 AI Integration**: Vercel AI SDK with OpenAI support
+- **🤖 AI Integration**: Vercel AI SDK with OpenRouter (access to 100+ AI models)
 - **🎨 UI Components**: shadcn/ui with Tailwind CSS
 - **⚡ Modern Stack**: Next.js 15, React 19, TypeScript
 - **📱 Responsive**: Mobile-first design approach
@@ -105,9 +105,11 @@ BETTER_AUTH_SECRET="your-random-32-character-secret-key-here"
 GOOGLE_CLIENT_ID="your-google-client-id"
 GOOGLE_CLIENT_SECRET="your-google-client-secret"
 
-# AI Integration (Optional - for chat functionality)
-OPENAI_API_KEY="sk-your-openai-api-key-here"
-OPENAI_MODEL="gpt-5-mini"
+# AI Integration via OpenRouter (Optional - for chat functionality)
+# Get your API key from: https://openrouter.ai/settings/keys
+# View available models at: https://openrouter.ai/models
+OPENROUTER_API_KEY="sk-or-v1-your-openrouter-api-key-here"
+OPENROUTER_MODEL="openai/gpt-5-mini"
 
 # App URL (for production deployments)
 NEXT_PUBLIC_APP_URL="http://localhost:3000"
@@ -152,13 +154,14 @@ Your application will be available at [http://localhost:3000](http://localhost:3
    - `https://yourdomain.com/api/auth/callback/google` (production)
 6. Copy the **Client ID** and **Client Secret** to your `.env` file
 
-### OpenAI API Key
+### OpenRouter API Key
 
-1. Go to <a href="https://platform.openai.com/dashboard" target="_blank">OpenAI Platform</a>
-2. Navigate to **API Keys** in the sidebar
-3. Click **Create new secret key**
-4. Give it a name and copy the key
-5. Add it to your `.env` file as `OPENAI_API_KEY`
+1. Go to <a href="https://openrouter.ai/" target="_blank">OpenRouter</a>
+2. Sign up or log in to your account
+3. Navigate to **Settings** → **Keys** or visit <a href="https://openrouter.ai/settings/keys" target="_blank">Keys Settings</a>
+4. Click **Create Key** and give it a name
+5. Copy the API key and add it to your `.env` file as `OPENROUTER_API_KEY`
+6. Browse available models at <a href="https://openrouter.ai/models" target="_blank">OpenRouter Models</a>
 
 ## 🗂️ Project Structure
 
@@ -201,7 +204,7 @@ npm run db:reset     # Reset database (drop all tables)
 
 - **Home (`/`)**: Landing page with setup instructions and features overview
 - **Dashboard (`/dashboard`)**: Protected user dashboard with profile information
-- **Chat (`/chat`)**: AI-powered chat interface using OpenAI (requires authentication)
+- **Chat (`/chat`)**: AI-powered chat interface using OpenRouter (requires authentication)
 
 ## 🚀 Deployment
 
@@ -230,8 +233,8 @@ Ensure these are set in your production environment:
 - `BETTER_AUTH_SECRET` - Secure random 32+ character string
 - `GOOGLE_CLIENT_ID` - Google OAuth Client ID
 - `GOOGLE_CLIENT_SECRET` - Google OAuth Client Secret
-- `OPENAI_API_KEY` - OpenAI API key (optional)
-- `OPENAI_MODEL` - OpenAI model name (optional, defaults to gpt-5-mini)
+- `OPENROUTER_API_KEY` - OpenRouter API key (optional, for AI chat functionality)
+- `OPENROUTER_MODEL` - Model name from OpenRouter (optional, defaults to openai/gpt-5-mini)
 - `NEXT_PUBLIC_APP_URL` - Your production domain
 
 ## 🎥 Tutorial Video