Implement comprehensive LLM provider system with global cost protection

- Add multi-provider LLM architecture supporting OpenRouter, OpenAI, Gemini, and custom providers
- Implement global LLM on/off switch with default DISABLED state for cost protection
- Add per-character LLM configuration with provider-specific models and settings
- Create performance-optimized caching system for LLM enabled status checks
- Add API key validation before enabling LLM providers to prevent broken configurations
- Implement audit logging for all LLM enable/disable actions for cost accountability
- Create comprehensive admin UI with prominent cost warnings and confirmation dialogs
- Add visual indicators in character list for custom AI model configurations
- Build character-specific LLM client system with global fallback mechanism
- Add database schema support for per-character LLM settings
- Implement graceful fallback responses when LLM is globally disabled
- Create provider testing and validation system for reliable connections

.env.example

@@ -35,7 +35,7 @@ LLM_API_KEY=x
 LLM_TIMEOUT=300
 LLM_MAX_TOKENS=2000
 LLM_TEMPERATURE=0.8
-LLM_MAX_PROMPT_LENGTH=6000
+LLM_MAX_PROMPT_LENGTH=16000
 LLM_MAX_HISTORY_MESSAGES=5
 LLM_MAX_MEMORIES=5
 
@@ -46,6 +46,29 @@ ADMIN_USERNAME=admin
 ADMIN_PASSWORD=FIre!@34
 SECRET_KEY=CAKUZ5ds49B1PUEWDWt07TdgxjTtDvvxOOkvOOfbnDE
 
+# LLM Provider Configuration
+# OpenRouter (supports Claude, GPT, Llama, etc.)
+OPENROUTER_ENABLED=false
+OPENROUTER_API_KEY=
+OPENROUTER_MODEL=anthropic/claude-3-sonnet
+
+# OpenAI
+OPENAI_ENABLED=false
+OPENAI_API_KEY=
+OPENAI_MODEL=gpt-4o-mini
+
+# Google Gemini
+GEMINI_ENABLED=false
+GEMINI_API_KEY=
+GEMINI_MODEL=gemini-1.5-flash
+
+# Custom/Local LLM (current setup)
+CUSTOM_LLM_ENABLED=true
+
+# Ollama
+OLLAMA_ENABLED=false
+OLLAMA_MODEL=llama3
+
 # System Configuration
 CONVERSATION_FREQUENCY=0.5
 RESPONSE_DELAY_MIN=1.0