feat: add Ollama local LLM support with optional API key

[Dreichi]

Add Ollama Local LLM Support

🚀 Features

• Local LLM Integration: Added comprehensive Ollama support for local AI inference
• Optional API Key: Ollama can work without API key for local deployments
• Unified JSON Forcing: Created llmClient.ts for consistent JSON formatting across providers
• Multi-Provider Support: Seamless switching between Gemini, OpenAI, and Ollama

🔧 Technical Implementation

• New Services:
  • OllamaService: Full-featured service with all AI operations
  • llmClient.ts: Unified client with automatic JSON forcing (format: "json" for Ollama)
  • unifiedAIService.ts: Factory pattern for provider abstraction
• UI Enhancement: Updated ConfigDialog with Ollama configuration options
• Type Safety: Extended config store to support 'ollama' provider type
• Smart Validation: Optional API key validation (required for Gemini/OpenAI, optional for Ollama)

🌍 Internationalization

• Added translation keys for Ollama-specific UI elements
• Support for both English and Chinese locales
• Consistent labeling across all providers

🎉 Benefits for Users

• 💰 Cost Reduction: Run AI locally without API costs
• 🔒 Privacy: No data sent to external services
• ⚡ Performance: Direct local inference without network latency
• 🔧 Flexibility: Support for any Ollama-compatible model (llama2, mistral, etc.)
• 🌐 Accessibility: Works offline once models are downloaded

🔄 Backward Compatibility

• All existing Gemini and OpenAI integrations remain unchanged
• No breaking changes to existing user configurations
• Seamless migration path for current users

[SSShooter]

Most of the code in src/services/ollamaService.ts is duplicated with src/services/geminiService.ts. It should only be necessary to extend the functionality of geminiService.