Add Meeting system subject and notification system

- Auto-create a locked "Meeting" subject for every user on registration
  and seed it for all existing users on startup
- Meeting subject cannot be deleted or renamed (is_system flag)
- 5-minute corner toast warning on Dashboard and TV with live countdown,
  dismiss button, and 1-minute re-notify if dismissed
- At start time: full-screen TV overlay with 30-second auto-dismiss,
  automatic pause of running block, switch to Meeting block, and
  auto-start of Meeting timer
- Web Audio API chimes: rising on warnings, falling at meeting start
- Update README with Meeting subject and notification system docs

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

backend/app/main.py

@@ -2,12 +2,15 @@ from contextlib import asynccontextmanager
 
 from fastapi import FastAPI, WebSocket, WebSocketDisconnect
 from fastapi.middleware.cors import CORSMiddleware
-from sqlalchemy import text
+from sqlalchemy import select, text
 from sqlalchemy.exc import OperationalError
+from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.config import get_settings
 from app.database import engine
 from app.models import Base
+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.websocket.manager import manager
@@ -35,6 +38,27 @@ async def lifespan(app: FastAPI):
         await _add_column_if_missing(conn, "schedule_blocks", "break_time_minutes", "INT NULL")
         await _add_column_if_missing(conn, "children", "strikes", "INT NOT NULL DEFAULT 0")
         await _add_column_if_missing(conn, "users", "timezone", "VARCHAR(64) NOT NULL DEFAULT 'UTC'")
+        await _add_column_if_missing(conn, "subjects", "is_system", "TINYINT(1) NOT NULL DEFAULT 0")
+
+    # Seed Meeting system subject for any existing users who don't have one
+    from app.database import AsyncSessionLocal
+    async with AsyncSessionLocal() as db:
+        users_result = await db.execute(select(User).where(User.is_active == True))
+        all_users = users_result.scalars().all()
+        for user in all_users:
+            existing = await db.execute(
+                select(Subject).where(Subject.user_id == user.id, Subject.is_system == True)
+            )
+            if not existing.scalar_one_or_none():
+                db.add(Subject(
+                    user_id=user.id,
+                    name="Meeting",
+                    icon="📅",
+                    color="#6366f1",
+                    is_system=True,
+                ))
+        await db.commit()
+
     yield
 
 

backend/app/models/subject.py

@@ -12,6 +12,7 @@ class Subject(TimestampMixin, Base):
     color: Mapped[str] = mapped_column(String(7), default="#10B981")  # hex color
     icon: Mapped[str] = mapped_column(String(10), default="📚")       # emoji
     is_active: Mapped[bool] = mapped_column(Boolean, default=True)
+    is_system: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
 
     user: Mapped["User"] = relationship("User", back_populates="subjects")  # noqa: F821
     schedule_blocks: Mapped[list["ScheduleBlock"]] = relationship(  # noqa: F821

backend/app/routers/auth.py

@@ -11,6 +11,7 @@ from app.auth.jwt import (
 )
 from app.dependencies import get_db
 from app.models.user import User
+from app.models.subject import Subject
 from app.schemas.auth import LoginRequest, RegisterRequest, TokenResponse
 from app.schemas.user import UserOut
 
@@ -39,6 +40,16 @@ async def register(body: RegisterRequest, response: Response, db: AsyncSession =
     await db.commit()
     await db.refresh(user)
 
+    meeting = Subject(
+        user_id=user.id,
+        name="Meeting",
+        icon="📅",
+        color="#6366f1",
+        is_system=True,
+    )
+    db.add(meeting)
+    await db.commit()
+
     access = create_access_token({"sub": str(user.id)})
     refresh = create_refresh_token({"sub": str(user.id)})
     response.set_cookie(REFRESH_COOKIE, refresh, **COOKIE_OPTS)

backend/app/routers/subjects.py

@@ -101,6 +101,8 @@ async def delete_subject(
     subject = result.scalar_one_or_none()
     if not subject:
         raise HTTPException(status_code=404, detail="Subject not found")
+    if subject.is_system:
+        raise HTTPException(status_code=403, detail="System subjects cannot be deleted")
     await db.delete(subject)
     await db.commit()
 

backend/app/schemas/subject.py

@@ -37,6 +37,7 @@ class SubjectOut(BaseModel):
     color: str
     icon: str
     is_active: bool
+    is_system: bool = False
     options: list[SubjectOptionOut] = []
 
     model_config = {"from_attributes": True}