fix: pass request.app (not registry.settings) to capture_karaoke_config

KeyError 'bucket.secure_uploads.region' in the detached karaoke child
on prod. production.ini stores keys with the app. prefix
(app.bucket.secure_uploads.region) and a request hook strips that
prefix into a dict attached as request.app. request.registry.settings
still carries the raw, prefixed keys.

The upload-time and on-demand karaoke call sites were passing
request.registry.settings; capture_karaoke_config expected the
stripped dict. Dev .ini happens to match both layouts which masked
this — prod raised KeyError and the response 502'd.

Switch both call sites to request.app (matches the pattern used by
backfill_karaoke_async and backfill_mirror_async) and document the
expected shape on capture_karaoke_config.

make_post_sell/lib/karaoke.py

@@ -302,6 +302,9 @@ def capture_karaoke_config(shop, app_settings):
     grandchild process receives only immutable values — no DB reads
     required until the final metadata write (after karaoke completes,
     minutes later, by which time the parent has long committed).
+
+    app_settings: the app-prefix-stripped settings dict — i.e. request.app
+    (NOT request.registry.settings, which keeps the "app." prefix in prod).
     """
     if shop.has_primary_s3:
         s3_creds = {

make_post_sell/views/product.py

@@ -465,7 +465,7 @@ def product_edit(request):
                 file_key=file_key,
                 extension=ext,
                 s3_path=product.s3_path,
-                karaoke_config=capture_karaoke_config(shop, request.registry.settings),
+                karaoke_config=capture_karaoke_config(shop, request.app),
                 db_url=str(request.dbsession.get_bind().url),
             )
 

make_post_sell/views/watch.py

@@ -286,7 +286,7 @@ def karaoke_process(request):
         file_key=file_key,
         extension=extension,
         s3_path=product.s3_path,
-        karaoke_config=capture_karaoke_config(shop, request.registry.settings),
+        karaoke_config=capture_karaoke_config(shop, request.app),
         db_url=str(request.dbsession.get_bind().url),
     )
     return {"status": "processing"}