feat: add comprehensive Session Analytics modal (Beta)

Added detailed analytics modal for each chat session including:
- Overview metrics (messages, tokens, tools, models, cache efficiency)
- Token usage breakdown with cost estimation
- Session timeline with duration tracking
- Time breakdown (Claude execution vs user conversing)
- Model information with usage percentages and message counts
- Tool usage statistics
- Components used (agents, slash commands, skills)

Key features:
- Real-time analytics calculation from JSONL conversation files
- Multi-model usage detection (Sonnet/Haiku switching)
- Intelligent time filtering (excludes long breaks)
- Cost estimation based on Claude API pricing
- Component detection from tool_use blocks

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: davila7