Add Rate Monitor app — Booking.com + direct booking engine competitor rates

Combines Booking.com Playwright scraper (from forecasting), direct booking
engine scraper (ported from laptop-archive/guestline-monitor), and Newbook
own-hotel rates into one focused tool. Four views: Bookability, Market View
(with price index badges + direct rate sub-rows), Direct Rates (per-competitor
room breakdown, min-stay flags, hotel config/discovery), Rate Analysis
(advance purchase curve, DOW chart, rate timeline, comparison table).

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

backend/database.py

@@ -0,0 +1,37 @@
+"""
+Database connection and session management
+"""
+import os
+from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
+from sqlalchemy.orm import sessionmaker, declarative_base
+from sqlalchemy import create_engine
+
+DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://rates:rates_secret@localhost:5432/rates_db")
+
+ASYNC_DATABASE_URL = DATABASE_URL.replace("postgresql://", "postgresql+asyncpg://")
+
+async_engine = create_async_engine(ASYNC_DATABASE_URL, echo=False)
+AsyncSessionLocal = sessionmaker(
+    async_engine, class_=AsyncSession, expire_on_commit=False
+)
+
+sync_engine = create_engine(DATABASE_URL)
+SyncSessionLocal = sessionmaker(bind=sync_engine)
+
+Base = declarative_base()
+
+
+async def get_db():
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+def get_sync_db():
+    db = SyncSessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()