Use high-res images and return all photos in GeoJSON

- Use maxSizeUrl instead of url for photo URLs (highest available
  resolution from Rightmove)
- Remove 5-photo cap in GeoJSON export — return all available photos
- Apply same fix to both streaming and model-based export paths,
  and to the listing detail API endpoint

api/app.py

@@ -604,14 +604,14 @@ async def get_listing_detail(
     text_info = property_info.get("text", {})
     description = text_info.get("description") if isinstance(text_info, dict) else None
 
-    # Extract photos
+    # Extract photos (prefer high-res maxSizeUrl)
     photos_raw = property_info.get("images", [])
     photos: list[dict] = []
     if isinstance(photos_raw, list):
         for img in photos_raw:
             if isinstance(img, dict):
                 photos.append({
-                    "url": img.get("url", ""),
+                    "url": img.get("maxSizeUrl") or img.get("url", ""),
                     "caption": img.get("caption", ""),
                     "type": img.get("type", ""),
                 })