Add formations feature for drawing trendlines and channels on charts:
Backend (Formations.py):
- CRUD operations with DataCache integration
- Database table with scope-based indexing
- Line value calculation with infinite extension
- Property value lookup for strategy integration
Frontend (formations.js, formation_overlay.js):
- Three-class pattern: UIManager, DataManager, Controller
- SVG overlay for drawing with RAF sync loop
- Click-to-draw interface with temp line preview
- Anchor dragging for line adjustment
- Coordinate conversion using v5 API
UI Integration:
- HUD panel with Line/Channel buttons
- Formation cards with hover details
- Drawing controls (name input, save/cancel)
Socket handlers for real-time sync:
- request_formations, new_formation
- edit_formation, delete_formation
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
