Move trace project to root and rebrand from fnote

- Move all project files from `trace/` subdirectory to the repository root
- Rename directory structure from `fnote` to `trace`
- Update package references and imports (fnote -> trace)
- Update application branding and storage paths (~/.trace)
- Update build script and documentation
- Ensure __pycache__ is ignored

main.py

@@ -0,0 +1,4 @@
+from trace.cli import main
+
+if __name__ == "__main__":
+    main()