fix: raise face detection threshold to 0.85, tighten clustering

Eliminates false positives (dog faces, painting faces) by requiring
score >= 0.85. Tighten cluster eps to 0.25 for better separation.
Tested: 4 real faces from 2 photos, no false positives.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mulita.yml

@@ -44,6 +44,6 @@ vision:
   faces:
     enabled: true
     min_face_size: 40
-    recognition_threshold: 0.7
-    cluster_eps: 0.35
+    recognition_threshold: 0.85
+    cluster_eps: 0.25
   worker_concurrency: 2