fix: remove root app.py — HF defaults to app.py over app_file setting

app.py

@@ -1,18 +0,0 @@
-import streamlit as st
-import sys, os, traceback
-from pathlib import Path
-
-root = Path(__file__).resolve().parent
-sys.path.insert(0, str(root))
-os.chdir(str(root))
-
-try:
-    demo = root / "demo" / "streamlit_app.py"
-    with open(demo, encoding="utf-8") as f:
-        code = f.read()
-    exec(compile(code, str(demo), "exec"), {"__file__": str(demo), "__name__": "__main__"})
-except SystemExit:
-    pass
-except BaseException as e:
-    st.error(f"SpindleFlow failed to load: {e}")
-    st.code(traceback.format_exc())