fix(api): surface each device's own catalog category per-match

The per-device entries in an upload's matched_devices list were labelled
with the ML overall predicted_category, producing contradictions like
"Acurite Tower Sensor -> Fan Controller". The engine now preserves each
DeviceMatch's true catalog category in match_details["device_category"],
and the API surfaces that per device. The headline device_category still
reflects the ML overall call, so the honest gate-metric category is
unchanged.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/matcher/engine.py

@@ -87,7 +87,14 @@ class SignatureMatcher:
                     manufacturer=device_match.manufacturer or "Unknown",
                     confidence=device_match.confidence,
                     match_method=device_match.match_method,
-                    match_details=device_match.details
+                    # Preserve each device's own catalog category so the API can
+                    # surface it per-device (e.g. an Acurite sensor stays
+                    # "Weather Sensor"); the ML overall call remains in the
+                    # match_details' predicted_category.
+                    match_details={
+                        **device_match.details,
+                        "device_category": device_match.category,
+                    }
                 ))
 
             return match_results