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/services/scraper_backends/base.py

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+"""
+Abstract base class for booking.com scraper backends.
+
+Defines the interface that all scraper backends must implement,
+allowing easy switching between local Playwright, proxied Playwright,
+or external services like Apify.
+"""
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass, field
+from datetime import date
+from decimal import Decimal
+from typing import List, Optional, Dict, Any
+from enum import Enum
+
+
+class AvailabilityStatus(str, Enum):
+    """Availability status for a hotel rate."""
+    AVAILABLE = 'available'      # Rate found, bookable
+    SOLD_OUT = 'sold_out'        # Hotel shows no availability
+    NO_DATA = 'no_data'          # Couldn't determine (scraper issue)
+
+
+@dataclass
+class RateData:
+    """Rate data for a single hotel on a single date."""
+    hotel_id: Optional[str] = None       # Our internal hotel_id (filled after DB lookup)
+    booking_com_id: str = ''             # Hotel ID from booking.com
+    rate_date: date = None
+    availability_status: AvailabilityStatus = AvailabilityStatus.NO_DATA
+    rate_gross: Optional[Decimal] = None
+    currency: str = 'GBP'
+    room_type: Optional[str] = None
+    breakfast_included: Optional[bool] = None
+    free_cancellation: Optional[bool] = None
+    no_prepayment: Optional[bool] = None
+    rooms_left: Optional[int] = None     # "Only X rooms left"
+    available_qty: Optional[int] = None  # Future: from hotel page dropdown
+
+
+@dataclass
+class HotelData:
+    """Hotel data discovered from search results."""
+    booking_com_id: str
+    name: str
+    booking_com_url: Optional[str] = None
+    star_rating: Optional[Decimal] = None
+    review_score: Optional[Decimal] = None
+    review_count: Optional[int] = None
+
+
+@dataclass
+class ScraperResult:
+    """Result from a scraping operation."""
+    success: bool
+    blocked: bool = False                # True if anti-scrape blocking detected
+    block_reason: Optional[str] = None   # CAPTCHA, rate limit, etc.
+    hotels: List[HotelData] = field(default_factory=list)
+    rates: List[RateData] = field(default_factory=list)
+    error_message: Optional[str] = None
+    page_content_sample: Optional[str] = None  # For debugging
+
+
+class ScraperBackend(ABC):
+    """
+    Abstract base class for scraper backends.
+
+    All backends must implement these methods to provide a consistent
+    interface for the main booking_scraper.py service.
+    """
+
+    # Common block detection signals
+    BLOCK_SIGNALS = [
+        'captcha',
+        'unusual traffic',
+        'access denied',
+        'please verify',
+        'too many requests',
+        'are you a robot',
+        'verify you are human',
+        'security check',
+    ]
+
+    @abstractmethod
+    async def scrape_location_search(
+        self,
+        location: str,
+        check_in: date,
+        check_out: date,
+        adults: int = 2,
+        pages: int = 2
+    ) -> ScraperResult:
+        """
+        Scrape booking.com location search results.
+
+        Args:
+            location: Location name (e.g., "Bowness-on-Windermere")
+            check_in: Check-in date
+            check_out: Check-out date (typically check_in + 1 for single night)
+            adults: Number of adults for search
+            pages: Number of search result pages to scrape
+
+        Returns:
+            ScraperResult with hotels and rates found
+        """
+        pass
+
+    @abstractmethod
+    async def scrape_hotel_page(
+        self,
+        hotel_url: str,
+        check_in: date,
+        check_out: date,
+        adults: int = 2
+    ) -> ScraperResult:
+        """
+        Scrape an individual hotel page for detailed rates.
+
+        Future expansion - not used in initial implementation.
+        Will provide available_qty from room dropdowns.
+
+        Args:
+            hotel_url: Full booking.com URL for the hotel
+            check_in: Check-in date
+            check_out: Check-out date
+            adults: Number of adults
+
+        Returns:
+            ScraperResult with detailed rate information
+        """
+        pass
+
+    @abstractmethod
+    async def close(self):
+        """Clean up any resources (browser instances, etc.)."""
+        pass
+
+    def detect_blocking(self, page_content: str) -> tuple[bool, Optional[str]]:
+        """
+        Check if page content shows anti-scrape response.
+
+        Args:
+            page_content: HTML content of the page
+
+        Returns:
+            Tuple of (is_blocked, reason)
+        """
+        content_lower = page_content.lower()
+        for signal in self.BLOCK_SIGNALS:
+            if signal in content_lower:
+                return True, signal
+        return False, None