Refactor local Makefile to run relevant things before tests/devserver

Summary:
The tests now depend on webpack being built, so do that before running make
test.

The devserver depends on migrations being run, so do that as well.

I'm not entirely sure the migration part is the right thing to do, but at least
with the webpack part, running the tests will do reasonable things.

Test Plan: make test still works

Reviewers: anlambert, Reviewers!

Differential Revision: https://forge.softwareheritage.org/D320