Add Rules & Expectations feature with TV overlay and dashboard layout updates

- Add Rules & Expectations admin section with drag-to-reorder, add/edit/delete
- Add Overlays card to Dashboard with Rules/Expectations toggle button (LIVE badge when active)
- Add full-screen rules overlay on TV view (green theme, numbered list, tap to dismiss)
- Backend: new RuleItem model, /api/rules CRUD + bulk reorder, /api/overlays WS broadcast endpoints
- Schedule store handles show_rules / hide_rules WebSocket events
- Rearrange Dashboard top row: TV Dashboard | 3 Strikes | Overlays (3-col, mobile stacks)
- Put Today's Session and Today's Schedule side-by-side at 50/50 width (mobile stacks)
- Update README with all new features, setup steps, WS events, and project structure

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/main.py

@@ -14,7 +14,7 @@ from app.models.child import Child
 from app.models.subject import Subject
 from app.models.user import User
 from app.routers import auth, users, children, subjects, schedules, sessions, logs, dashboard
-from app.routers import morning_routine, break_activity, admin
+from app.routers import morning_routine, break_activity, admin, rules, overlays
 from app.websocket.manager import manager
 
 settings = get_settings()
@@ -113,6 +113,8 @@ app.include_router(morning_routine.router)
 app.include_router(break_activity.router)
 app.include_router(dashboard.router)
 app.include_router(admin.router)
+app.include_router(rules.router)
+app.include_router(overlays.router)
 
 
 @app.get("/api/health")