Restructure scripts into dev/ and prod/ for the devcontainer

- scripts/prod: entrypoint, db-setup and schema.sql shipped in the image
- scripts/dev: seed/clear db, psql and cleanup, run natively in the
  devcontainer instead of via docker-compose
- move setup.cfg to the repo root so linters pick it up
- Makefile targets run directly in the devcontainer

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

setup.cfg

@@ -0,0 +1,13 @@
+[flake8]
+max_line_length = 96
+
+[isort]
+include_trailing_comma = true
+multi_line_output = 3
+lines_after_imports = 2
+combine_as_imports = true
+force_grid_wrap = 0
+use_parentheses = true
+line_length = 88
+known_first_party = max
+known_third_party = flask