Enhance chat panel with session stats and improved UI

[rg4444]

Summary

This PR enhances the ChatPanel component with comprehensive session statistics tracking and improves the user interface with better styling and localization support.

Key Changes

Session Statistics Tracking:

• Added sessionStats ref to track conversation metrics: turns, total tokens, total cost, and tools called
• Updated status bar to display aggregated session statistics instead of just the last message
• Statistics are reset when starting a new conversation

LLM Configuration:

• Added llm config type with model field to support dynamic model names
• Updated modelName computed property to parse model names from config and strip version suffixes (e.g., "claude-sonnet-4-5" → "Sonnet")

UI Improvements:

• Refactored tool calls display from expandable details to compact chips with improved styling
• Moved quick questions section above the input area and made it conditional (only show when no messages exist)
• Updated status bar with better emoji indicators and monospace font for metrics
• Improved quick question button styling with hover effects and better color scheme
• Enhanced header subtitle styling with adjusted opacity and spacing

Localization:

• Changed welcome message from English to Latvian: "Sveiki! Es esmu {agentName}. Kā varu palīdzēt?"

Cost Estimation Updates:

• Adjusted Claude Opus pricing rates in both Go implementations (integration tests and router):
  • Input rate: 15.0 → 5.0 per million tokens
  • Output rate: 75.0 → 25.0 per million tokens

Validation

• No BPMN render/diff impact
• No image regeneration needed
• No schema/validator updates required

Testing

Existing integration tests updated and passing:

• TestEstimateCost in modules/chat/integration_test.go validates cost estimation with updated Opus pricing
• Manual verification of chat panel functionality with session statistics tracking

https://claude.ai/code/session_015oJpLxdf2NXp7UbYMD1yaY