fix(mcs150 pdf): set /NeedAppearances so filled field values actually render

Customer saw the MCS-150 looking blank / 'data covered by the form fields': the
values were correctly written to the AcroForm /V, but pypdf left the template's
empty /AP appearance streams in place and NeedAppearances was false, so viewers
rendered the blank widget over the value. Setting AcroForm /NeedAppearances=true
makes viewers regenerate appearances from the values. (The missing signature was
a downstream effect of the separate fobj_put MinIO-upload bug, now fixed -- with
no PDF in MinIO the anchor extraction + signature stamping both failed.)

scripts/document_gen/templates/mcs150_pdf_filler.py

@@ -245,6 +245,20 @@ def fill_mcs150(intake: dict, order_number: str = "") -> str:
             except Exception as e:
                 LOG.debug("Checkbox %s set failed: %s", field_name, e)
 
+    # Force viewers to (re)generate field appearance streams from the values we
+    # set. Without /NeedAppearances, pypdf leaves the template's blank /AP streams
+    # in place, so the typed values are present in /V but the viewer renders the
+    # empty widget on top -- the data looks missing / "covered up by the form
+    # field". Setting NeedAppearances=true on the AcroForm fixes the rendering.
+    try:
+        catalog = writer._root_object
+        if "/AcroForm" in catalog:
+            acro = catalog["/AcroForm"]
+            acro_obj = acro.get_object() if hasattr(acro, "get_object") else acro
+            acro_obj[NameObject("/NeedAppearances")] = BooleanObject(True)
+    except Exception as exc:
+        LOG.warning("Could not set NeedAppearances: %s", exc)
+
     # Save
     work_dir = tempfile.mkdtemp(prefix="pw_mcs150_")
     dot = intake.get("dot_number", "unknown")