Refactor into standard Python package with uv

- Move all code into src/mouse_control/ following the src-layout convention,
  with model/collect/train/visualize/inference as separate modules and
  SimpleNet extracted into model.py
- Add hatchling-based pyproject.toml with three CLI entry points
  (mouse-collect, mouse-train, mouse-visualize) and bundle the trained
  ONNX model as a package resource under assets/
- Move training data to data/, delete superseded show.py, remove dead
  imports (numpy, onnxruntime, onnx, onnxsim) and the unused
  visualize_path() helper
- Fix crashes in the collector: guard against destroyed-widget access
  after the n==100 destroy(), and skip save_to_csv when recording is
  off or the path is too short to derive 10 keypoints
- Switch ONNX export to external_data=False so the model ships as a
  single self-contained 19KB file
- Bytes-load the bundled model via importlib.resources so packaging
  remains correct under zip-safe distributions
- Rewrite README around the new layout, commands, and public API

data/mouse_data_test.csv

@@ -0,0 +1,20 @@
+"-122,-17","0,0","-3,-3","-9,-7","-19,-11","-32,-16","-51,-19","-68,-20","-84,-20","-102,-19","-114,-17"
+"-115,-153","0,0","-10,-13","-34,-62","-68,-105","-74,-128","-78,-139","-82,-147","-89,-152","-98,-155","-107,-156"
+"-77,193","0,0","-2,9","-12,31","-26,68","-41,106","-54,136","-63,156","-67,170","-71,178","-75,183"
+"-85,-86","0,0","-5,-5","-20,-19","-47,-36","-69,-50","-80,-57","-85,-61","-85,-66","-85,-71","-85,-77"
+"29,-175","0,0","9,-10","25,-51","32,-90","30,-119","30,-138","30,-146","29,-152","33,-165","36,-175"
+"-201,197","0,0","-12,20","-64,77","-113,129","-130,160","-139,175","-152,178","-171,181","-184,183","-191,187"
+"-124,-16","0,0","-6,-1","-20,-4","-42,-8","-67,-13","-90,-16","-109,-19","-116,-21","-119,-20","-122,-18"
+"-123,53","0,0","-16,7","-47,17","-73,22","-92,24","-106,29","-109,32","-112,38","-115,45","-118,49"
+"-146,-125","0,0","0,-12","-12,-40","-33,-58","-64,-84","-95,-115","-116,-123","-126,-125","-134,-122","-141,-122"
+"132,49","0,0","9,5","32,11","56,18","81,30","95,36","102,39","108,41","114,44","123,48"
+"157,164","0,0","9,10","36,35","72,68","107,97","132,121","146,137","149,145","151,152","154,158"
+"-52,48","0,0","-5,5","-14,11","-20,18","-26,24","-29,30","-30,36","-31,41","-32,47","-40,48"
+"-135,-106","0,0","-13,-15","-34,-37","-56,-61","-75,-78","-86,-90","-93,-98","-99,-104","-104,-105","-116,-107"
+"197,99","0,0","3,6","23,21","62,33","111,48","157,63","177,74","181,82","184,86","192,91"
+"129,-194","0,0","7,-7","19,-26","45,-55","77,-85","104,-117","117,-139","118,-149","119,-162","123,-180"
+"167,-56","0,0","14,-6","42,-15","79,-23","115,-31","138,-39","149,-45","152,-48","155,-50","159,-51"
+"132,143","0,0","28,4","84,24","113,57","116,77","118,88","120,98","120,107","122,124","126,135"
+"-113,89","0,0","-11,8","-38,23","-71,41","-81,48","-86,56","-89,62","-92,67","-97,73","-103,79"
+"-46,-8","0,0","-2,1","-4,1","-7,1","-11,0","-16,-2","-24,-4","-30,-5","-35,-7","-39,-8"
+"-40,181","0,0","0,37","-11,92","-12,120","-12,133","-12,148","-14,168","-21,178","-25,184","-32,184"