svc-vision: camera live view, moved from app-flutter's test tool

Camera-agnostic (--camera auto finds any V4L2 capture device and finds it
again after a replug; non-MJPEG cameras are encoded), says when the camera
is unavailable, paced per decision 28. Python, standard library only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

.editorconfig

@@ -0,0 +1,20 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+
+[*.{rs,toml}]
+indent_size = 4
+
+[*.{dart,json,yaml,yml}]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.py]
+indent_size = 4