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/routers/overlays.py

@@ -0,0 +1,56 @@
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy import select
+
+from app.dependencies import get_db, get_current_user
+from app.models.child import Child
+from app.models.rule import RuleItem
+from app.models.user import User
+from app.websocket.manager import manager
+
+router = APIRouter(prefix="/api/overlays", tags=["overlays"])
+
+
+class ChildTarget(BaseModel):
+    child_id: int
+
+
+async def _verify_child(child_id: int, user: User, db: AsyncSession) -> Child:
+    result = await db.execute(
+        select(Child).where(Child.id == child_id, Child.user_id == user.id)
+    )
+    child = result.scalar_one_or_none()
+    if not child:
+        raise HTTPException(status_code=404, detail="Child not found")
+    return child
+
+
+@router.post("/rules/show")
+async def show_rules_overlay(
+    body: ChildTarget,
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    child = await _verify_child(body.child_id, current_user, db)
+
+    rules_result = await db.execute(
+        select(RuleItem)
+        .where(RuleItem.user_id == current_user.id)
+        .order_by(RuleItem.order_index, RuleItem.id)
+    )
+    rules = [item.text for item in rules_result.scalars().all()]
+
+    await manager.broadcast(child.id, {"event": "show_rules", "rules": rules})
+    return {"ok": True}
+
+
+@router.post("/rules/hide")
+async def hide_rules_overlay(
+    body: ChildTarget,
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    child = await _verify_child(body.child_id, current_user, db)
+    await manager.broadcast(child.id, {"event": "hide_rules"})
+    return {"ok": True}