feat: wire Sam21Client into _deps and config

Adds services.sam21 (base_url + timeout_s) and grasp.use_sam21 toggle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

config.yaml

@@ -17,6 +17,9 @@ services:
     base_url: http://localhost:8767
     timeout_s: 5.0
     write_timeout_s: 30.0
+  sam21:
+    base_url: http://localhost:8002
+    timeout_s: 10.0
 aruco:
   dictionary: DICT_4X4_50
   wrist_marker:
@@ -31,6 +34,7 @@ grasp:
   max_object_width_m: 0.08
   pointcloud_step: 1
   pointcloud_max_depth_mm: 2000
+  use_sam21: true
   visual_servo:
     min_distance_m: 0.1
     step_fraction: 0.5