Add time-based day progress bar to dashboards

Replaces block-count progress with a wall-clock progress bar driven by
configurable day start/end hours on each schedule template.

- ScheduleTemplate: add day_start_time / day_end_time (TIME, nullable)
- Startup migration: idempotent ALTER TABLE for existing DBs
- Dashboard snapshot: includes day_start_time / day_end_time from template
- Admin → Schedules: time pickers in block editor to set day hours
- Dashboard view: time-based progress bar with start/current/end labels
- TV view: full-width day progress strip between header and main content

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

backend/app/main.py

@@ -2,6 +2,8 @@ from contextlib import asynccontextmanager
 
 from fastapi import FastAPI, WebSocket, WebSocketDisconnect
 from fastapi.middleware.cors import CORSMiddleware
+from sqlalchemy import text
+from sqlalchemy.exc import OperationalError
 
 from app.config import get_settings
 from app.database import engine
@@ -12,11 +14,23 @@ from app.websocket.manager import manager
 settings = get_settings()
 
 
+async def _add_column_if_missing(conn, table: str, column: str, definition: str):
+    """Add a column to a table, silently ignoring if it already exists (MySQL 1060)."""
+    try:
+        await conn.execute(text(f"ALTER TABLE {table} ADD COLUMN {column} {definition}"))
+    except OperationalError as e:
+        if e.orig.args[0] != 1060:  # 1060 = Duplicate column name
+            raise
+
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     # Create tables on startup (Alembic handles migrations in prod, this is a safety net)
     async with engine.begin() as conn:
         await conn.run_sync(Base.metadata.create_all)
+        # Idempotent column additions for schema migrations
+        await _add_column_if_missing(conn, "schedule_templates", "day_start_time", "TIME NULL")
+        await _add_column_if_missing(conn, "schedule_templates", "day_end_time", "TIME NULL")
     yield