feat: implement legacy shop management system and add task documentation files

.flake8

@@ -0,0 +1,18 @@
+[flake8]
+max-line-length = 80
+import-order-style = google
+application-import-names = shop
+exclude =
+    .git,
+    __pycache__,
+    build,
+    dist,
+    .venv,
+    venv,
+    .mypy_cache,
+    .pytest_cache
+ignore =
+    # N802: function name should be lowercase (we want the student to fix this, but standard pep8 has this. Let's not ignore it so they have to fix it!)
+    # T201, T001: print found (they will need prints for CLI, so we can ignore print check T201 if they use print check plugins, but default flake8 doesn't check prints unless we use flake8-print)
+    # We will keep it minimal so flake8 checks standard styling, naming, and import order.
+    E121, E123, E126, E226, E24, E704, W503, W504