Fix Guestline + Mews direct scrapers after engine API changes

Both competitor booking engines changed their API contracts, silently
breaking their direct scrapes ~16 days ago (200 responses with empty
bodies, so no exception was ever raised):

- Guestline: the /enhanced availability endpoint now returns a bare []
  for every date. Switch to the base /api/availabilities/{coll}/{hotel}
  endpoint, which returns {"rooms":[...]} with the same room shape.
- Mews: getAvailability now rejects the old body with "Invalid
  EnterpriseId" — it requires enterpriseId + serviceId. getPricing
  additionally requires currencyCode. Capture the enterprise's
  defaultCurrencyCode in _ensure_config and send all three.

Also stop last_scraped_at advancing when a run saves 0 rows, so the
overview no longer reports a phantom-fresh scrape while the per-date
data stays stale — the symptom that surfaced this.

Verified live: Three Ways now yields 41 rows/night, Old Stocks 10.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/services/direct_scraper.py

@@ -123,19 +123,25 @@ def run_scrape(hotel_id: int, profile_name: str, params: dict):
 
     loop = asyncio.new_event_loop()
     try:
-        loop.run_until_complete(_run_scrape_async(hotel_id, profile, params, scraped_at))
+        rows_saved = loop.run_until_complete(_run_scrape_async(hotel_id, profile, params, scraped_at))
     finally:
         loop.close()
 
-    db = SyncSessionLocal()
-    try:
-        db.execute(
-            text("UPDATE direct_competitor_hotels SET last_scraped_at = :ts WHERE id = :id"),
-            {"ts": scraped_at, "id": hotel_id}
-        )
-        db.commit()
-    finally:
-        db.close()
+    # Only advance last_scraped_at when the run actually captured data. A run that
+    # saved nothing means the engine returned empty/errored — don't let the overview
+    # report a phantom-fresh scrape while the per-date data stays stale.
+    if rows_saved:
+        db = SyncSessionLocal()
+        try:
+            db.execute(
+                text("UPDATE direct_competitor_hotels SET last_scraped_at = :ts WHERE id = :id"),
+                {"ts": scraped_at, "id": hotel_id}
+            )
+            db.commit()
+        finally:
+            db.close()
+    else:
+        log.warning(f"Hotel {hotel_id}: scrape saved 0 rows — last_scraped_at left unchanged")
 
 
 async def _run_scrape_async(hotel_id: int, profile, params: dict, scraped_at: datetime):
@@ -144,7 +150,7 @@ async def _run_scrape_async(hotel_id: int, profile, params: dict, scraped_at: da
             arrival_dates = await profile.fetch_arrival_dates(client, params)
         except Exception as e:
             log.error(f"Hotel {hotel_id}: failed to fetch arrival dates: {e}")
-            return
+            return 0
 
         log.info(f"Hotel {hotel_id}: {len(arrival_dates)} bookable dates")
 
@@ -305,3 +311,4 @@ async def _run_scrape_async(hotel_id: int, profile, params: dict, scraped_at: da
             db.close()
 
     log.info(f"Hotel {hotel_id}: scrape complete, {rows_saved} rows saved")
+    return rows_saved