Replace bloated requirements with minimal dependencies

The 400+ package requirements_manual.txt included packages like av
that need system libraries (FFmpeg) and aren't used by the app.
Install only the actually needed packages instead.

app.py

@@ -27,7 +27,7 @@ def setup_deps():
     run("pip install 'setuptools<81'")  # pin setuptools to keep pkg_resources available
     run("pip install torch==2.6.0 torchvision==0.21.0 torchaudio==2.6.0 --index-url https://download.pytorch.org/whl/cpu")
     run("pip install -e .", cwd="segment-anything-2")
-    run("pip install --no-deps -r requirements_manual.txt")
+    run("pip install gradio opencv-python-headless ultralytics matplotlib")
     run("git lfs install && git lfs pull", cwd=".")  # assuming checkpoints/mouse_yolo.pt is tracked
 
     # Relaunch the script with an env flag to avoid looping