build: add Makefile with standard targets for flamapy-dev tooling

flamapy-dev 'make test/lint/mypy' failed here because the repo had no
Makefile. Add one following the sibling repos' convention, adapted to
this repo's layout (app.py + flamapy namespace package).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: jagalindo

Makefile

@@ -0,0 +1,29 @@
+.ONESHELL:
+
+.PHONY: build
+build:
+	rm -rf dist
+	python -m build
+
+upload-testpypi:
+	python3 -m twine upload --repository testpypi dist/*
+
+upload-pypi:
+	python3 -m twine upload --repository pypi dist/*
+
+lint:
+	ruff check .
+
+mypy:
+	mypy app.py flamapy
+
+test:
+	python -m pytest -sv
+
+cov:
+	coverage run --source=flamapy,app -m pytest
+	coverage report
+	coverage html
+
+start:
+	./start-server.sh