Add interactive Chat with LLM interface to Web UI

Features:
- Real-time streaming chat interface (ChatGPT-like experience)
- Model selection: Text model (fast) or Vision model (image analysis)
- System prompt toggle: Chat with Miku's personality or raw LLM
- Mood selector: Choose from 14 different emotional states
- Full context integration: Uses complete miku_lore.txt, miku_prompt.txt, and miku_lyrics.txt
- Conversation memory: Maintains chat history throughout session
- Image upload support for vision model
- Horizontal scrolling tabs for responsive design
- Clear chat history functionality
- SSE (Server-Sent Events) for streaming responses
- Keyboard shortcuts (Ctrl+Enter to send)

Technical changes:
- Added POST /chat/stream endpoint in api.py with streaming support
- Updated ChatMessage model with mood, conversation_history, and image_data
- Integrated context_manager for proper Miku personality context
- Added Chat with LLM tab to index.html
- Implemented JavaScript streaming client with EventSource-like handling
- Added CSS for chat messages, typing indicators, and animations
- Made tab navigation horizontally scrollable for narrow viewports

CHAT_QUICK_START.md

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+# Chat Interface - Quick Start Guide
+
+## 🚀 Quick Start
+
+### Access the Chat Interface
+1. Open the Miku Control Panel in your browser
+2. Click on the **"💬 Chat with LLM"** tab
+3. Start chatting!
+
+## 📋 Configuration Options
+
+### Model Selection
+- **💬 Text Model**: Fast text conversations
+- **👁️ Vision Model**: Image analysis
+
+### System Prompt
+- **✅ Use Miku Personality**: Chat with Miku's character
+- **❌ Raw LLM**: Direct LLM without personality
+
+## 💡 Common Use Cases
+
+### 1. Chat with Miku
+```
+Model: Text Model
+System Prompt: Use Miku Personality
+Message: "Hi Miku! How are you feeling today?"
+```
+
+### 2. Test Raw LLM
+```
+Model: Text Model
+System Prompt: Raw LLM
+Message: "Explain quantum physics"
+```
+
+### 3. Analyze Images with Miku
+```
+Model: Vision Model
+System Prompt: Use Miku Personality
+Upload: [your image]
+Message: "What do you think of this image?"
+```
+
+### 4. Raw Image Analysis
+```
+Model: Vision Model
+System Prompt: Raw LLM
+Upload: [your image]
+Message: "Describe this image in detail"
+```
+
+## ⌨️ Keyboard Shortcuts
+- **Ctrl+Enter**: Send message
+
+## 🎨 Features
+- ✅ Real-time streaming (like ChatGPT)
+- ✅ Image upload for vision model
+- ✅ Color-coded messages
+- ✅ Timestamps
+- ✅ Typing indicators
+- ✅ Auto-scroll
+- ✅ Clear chat history
+
+## 🔧 System Prompts
+
+### Text Model with Miku
+- Full Miku personality
+- Current mood awareness
+- Character consistency
+
+### Vision Model with Miku
+- Miku analyzing images
+- Cheerful, playful descriptions
+
+### No System Prompt
+- Direct LLM responses
+- No character constraints
+
+## 📊 Message Types
+
+### User Messages (Green)
+- Your input
+- Right-aligned appearance
+
+### Assistant Messages (Blue)
+- Miku/LLM responses
+- Left-aligned appearance
+- Streams in real-time
+
+### Error Messages (Red)
+- Connection errors
+- Model errors
+- Clear error descriptions
+
+## 🎯 Tips
+
+1. **Use Ctrl+Enter** for quick sending
+2. **Select model first** before uploading images
+3. **Clear history** to start fresh conversations
+4. **Toggle system prompt** to compare responses
+5. **Wait for streaming** to complete before sending next message
+
+## 🐛 Troubleshooting
+
+### No response?
+- Check if llama.cpp is running
+- Verify network connection
+- Check browser console
+
+### Image not working?
+- Switch to Vision Model
+- Use valid image format (JPG, PNG)
+- Check file size
+
+### Slow responses?
+- Vision model is slower than text
+- Wait for streaming to complete
+- Check llama.cpp load
+
+## 📝 Examples
+
+### Example 1: Personality Test
+**With Miku Personality:**
+> User: "What's your favorite song?"
+> Miku: "Oh, I love so many songs! But if I had to choose, I'd say 'World is Mine' holds a special place in my heart! It really captures that fun, playful energy that I love! ✨"
+
+**Without System Prompt:**
+> User: "What's your favorite song?"
+> LLM: "I don't have personal preferences as I'm an AI language model..."
+
+### Example 2: Image Analysis
+**With Miku Personality:**
+> User: [uploads sunset image] "What do you see?"
+> Miku: "Wow! What a beautiful sunset! The sky is painted with such gorgeous oranges and pinks! It makes me want to write a song about it! The way the colors blend together is so dreamy and romantic~ 🌅💕"
+
+**Without System Prompt:**
+> User: [uploads sunset image] "What do you see?"
+> LLM: "This image shows a sunset landscape. The sky displays orange and pink hues. The sun is setting on the horizon. There are silhouettes of trees in the foreground."
+
+## 🎉 Enjoy Chatting!
+
+Have fun experimenting with different combinations of:
+- Text vs Vision models
+- With vs Without system prompts
+- Different types of questions
+- Various images (for vision model)
+
+The streaming interface makes it feel just like ChatGPT! 🚀