Pin Booking.com search to a dest_id

Free-text ss= destination resolution is non-deterministic: tonight's
30-day run resolved "Stow on the Wold" to St. Wolfgang, Austria for 8 of
30 dates, saving Salzkammergut hotel rates into the matrix. dest_id +
dest_type=city in the search URL pins the destination.

- booking_scrape_config gains a dest_id column (idempotent ALTER)
- scrape_location_search/_build_search_url thread dest_id through
- /config/location accepts dest_id

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/services/scraper_backends/base.py

@@ -90,7 +90,8 @@ class ScraperBackend(ABC):
         check_in: date,
         check_out: date,
         adults: int = 2,
-        pages: int = 2
+        pages: int = 2,
+        dest_id: Optional[str] = None
     ) -> ScraperResult:
         """
         Scrape booking.com location search results.
@@ -101,6 +102,9 @@ class ScraperBackend(ABC):
             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
+            dest_id: Booking.com numeric destination id. Pins the search to one
+                destination — free-text ss= resolves non-deterministically
+                (Stow on the Wold intermittently matched St. Wolfgang, Austria)
 
         Returns:
             ScraperResult with hotels and rates found

backend/services/scraper_backends/playwright_local.py

@@ -276,7 +276,8 @@ class PlaywrightLocalBackend(ScraperBackend):
         check_in: date,
         check_out: date,
         adults: int,
-        offset: int = 0
+        offset: int = 0,
+        dest_id: Optional[str] = None
     ) -> str:
         """Build booking.com search URL with parameters."""
         params = {
@@ -287,6 +288,11 @@ class PlaywrightLocalBackend(ScraperBackend):
             'no_rooms': 1,
             'group_children': 0,
         }
+        if dest_id:
+            # Pin the destination — without this, free-text ss= intermittently
+            # resolves to the wrong place entirely.
+            params['dest_id'] = dest_id
+            params['dest_type'] = 'city'
         if offset > 0:
             params['offset'] = offset
 
@@ -502,7 +508,8 @@ class PlaywrightLocalBackend(ScraperBackend):
         check_in: date,
         check_out: date,
         adults: int = 2,
-        pages: int = 2
+        pages: int = 2,
+        dest_id: Optional[str] = None
     ) -> ScraperResult:
         """
         Scrape booking.com location search results, rotating the proxy IP if
@@ -515,6 +522,7 @@ class PlaywrightLocalBackend(ScraperBackend):
             check_out: Check-out date (check_in + 1 for single night rate)
             adults: Number of adults
             pages: Number of result pages to scrape
+            dest_id: Booking.com numeric destination id (pins the search)
 
         Returns:
             ScraperResult with hotels and rates found
@@ -523,7 +531,7 @@ class PlaywrightLocalBackend(ScraperBackend):
         result = None
 
         for attempt in range(max_attempts):
-            result = await self._scrape_once(location, check_in, check_out, adults, pages)
+            result = await self._scrape_once(location, check_in, check_out, adults, pages, dest_id)
 
             # Soft-block signals: an explicit challenge, or a "successful" load
             # that yielded zero hotels (page 1 never rendered results).
@@ -547,7 +555,8 @@ class PlaywrightLocalBackend(ScraperBackend):
         check_in: date,
         check_out: date,
         adults: int,
-        pages: int
+        pages: int,
+        dest_id: Optional[str] = None
     ) -> ScraperResult:
         """A single scrape attempt for one date on the current IP/session."""
         all_hotels = []
@@ -574,7 +583,7 @@ class PlaywrightLocalBackend(ScraperBackend):
                 page_loaded = True
                 if page_num == 0:
                     # Navigate to page 1 by URL
-                    url = self._build_search_url(location, check_in, check_out, adults)
+                    url = self._build_search_url(location, check_in, check_out, adults, dest_id=dest_id)
                     logger.info(f"Scraping page {page_num + 1}: {url}")
                     try:
                         await page.goto(url, wait_until='domcontentloaded', timeout=30000)
@@ -588,7 +597,8 @@ class PlaywrightLocalBackend(ScraperBackend):
                     if not clicked:
                         # Fall back to offset URL if the control isn't found
                         url = self._build_search_url(
-                            location, check_in, check_out, adults, offset=page_num * 25
+                            location, check_in, check_out, adults,
+                            offset=page_num * 25, dest_id=dest_id
                         )
                         logger.info(f"Next-button not found, offset fallback: {url}")
                         try: