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/models/rule.py

@@ -0,0 +1,15 @@
+from sqlalchemy import ForeignKey, Integer, Text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.models.base import Base
+
+
+class RuleItem(Base):
+    __tablename__ = "rule_items"
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    text: Mapped[str] = mapped_column(Text, nullable=False)
+    order_index: Mapped[int] = mapped_column(Integer, default=0)
+
+    user: Mapped["User"] = relationship("User")  # noqa: F821