fix: don't collapse Amazon/BN format prices to single eBook label when credential set

Credentialed price fetch previously short-circuited before the multi-format
HTML parser and mislabeled every price as eBook. Now Amazon/Barnes & Noble
always attempt the full format-swatch parse first (Hardcover/eBook/Audiobook),
with the credential single price only as a fallback. Also stop guessing an
eBook binding for print/mixed retailers on the credential path.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/services/platform_pricing.py

@@ -467,11 +467,20 @@ async def fetch_listing_format_prices(
         return await _fetch_apple_format_prices(client, listing_url, ctx)
 
     # --- Credential-based platforms ---
-    if credential is not None:
+    # Amazon / Barnes & Noble expose ALL formats on their product page, so we
+    # skip the single-price credential shortcut for them and let the HTML
+    # multi-format parser run below. Only use credential fetch as a fallback
+    # (handled after the HTML attempt) so we never collapse 3 formats into 1.
+    _MULTI_FORMAT_HTML = {"amazon", "barnes_noble"}
+    if credential is not None and platform_id not in _MULTI_FORMAT_HTML:
         from app.services.platform_api_registry import fetch_price_via_credential
         hit = await fetch_price_via_credential(client, credential, platform_id, listing_url, ctx)
         if hit:
-            norm = canonical_format_prices({"eBook": hit.formatted}, platform_id)
+            fmt_key = _single_price_credential_format(platform_id)
+            norm = (
+                canonical_format_prices({fmt_key: hit.formatted}, platform_id)
+                if fmt_key else {}
+            )
             return FormatPriceHit(
                 format_prices=norm,
                 formatted=hit.formatted,
@@ -536,9 +545,33 @@ async def fetch_listing_format_prices(
                 platform=platform_id,
                 error=str(exc)[:120],
             )
+
+    # Amazon / BN HTML gave nothing (e.g. bot wall) — fall back to credential fetch.
+    if credential is not None and platform_id in _MULTI_FORMAT_HTML:
+        from app.services.platform_api_registry import fetch_price_via_credential
+        hit = await fetch_price_via_credential(client, credential, platform_id, listing_url, ctx)
+        if hit:
+            fmt_key = _single_price_credential_format(platform_id)
+            norm = (
+                canonical_format_prices({fmt_key: hit.formatted}, platform_id)
+                if fmt_key else {}
+            )
+            return FormatPriceHit(
+                format_prices=norm,
+                formatted=hit.formatted,
+                currency=hit.currency,
+            )
     return None
 
 
+def _single_price_credential_format(platform_id: str) -> str:
+    """Best-effort format label for a single credential price (empty if unknown)."""
+    if platform_id in {"kobo", "google_books"}:
+        return "eBook"
+    # Print-focused / mixed retailers: don't guess a binding.
+    return ""
+
+
 def _itunes_price_from_item(item: dict) -> tuple[str, str] | None:
     """Return (formatted_price, currency) from an iTunes lookup/search item."""
     raw_price = item.get("formattedPrice")