Add Google Gemini as AI provider

- Add gemini.py provider using google-genai SDK
- Update config.py with gemini provider and GEMINI_API_KEY
- Update ai_service.py factory to support gemini
- Add google-genai to requirements.txt
- Update .env.example, README.md, and CLAUDE.md documentation

README.md

@@ -4,7 +4,7 @@ A customizable Discord bot that responds to @mentions with AI-generated response
 
 ## Features
 
-- **Multi-Provider AI**: Supports OpenAI, OpenRouter, and Anthropic (Claude)
+- **Multi-Provider AI**: Supports OpenAI, OpenRouter, Anthropic (Claude), and Google Gemini
 - **Fully Customizable**: Configure bot name, personality, and behavior
 - **Conversation Memory**: Remembers context per user
 - **Easy Deployment**: Docker support included
@@ -50,10 +50,11 @@ All configuration is done via environment variables in `.env`.
 | Variable | Description |
 |----------|-------------|
 | `DISCORD_TOKEN` | Your Discord bot token |
-| `AI_PROVIDER` | `openai`, `openrouter`, or `anthropic` |
+| `AI_PROVIDER` | `openai`, `openrouter`, `anthropic`, or `gemini` |
 | `OPENAI_API_KEY` | OpenAI API key (if using OpenAI) |
 | `OPENROUTER_API_KEY` | OpenRouter API key (if using OpenRouter) |
 | `ANTHROPIC_API_KEY` | Anthropic API key (if using Anthropic) |
+| `GEMINI_API_KEY` | Google Gemini API key (if using Gemini) |
 
 ### Bot Identity
 
@@ -129,6 +130,7 @@ Mention the bot in any channel:
 | OpenAI | gpt-4o, gpt-4-turbo, gpt-3.5-turbo | Official OpenAI API |
 | OpenRouter | 100+ models | Access to Llama, Mistral, Claude, etc. |
 | Anthropic | claude-3-5-sonnet, claude-3-opus | Direct Claude API |
+| Gemini | gemini-2.0-flash, gemini-1.5-pro | Google AI API |
 
 ## Project Structure