Add the printedparts plugin: 3D-printed parts storefront and kiosk

Catalog with photos and append-only print-file revisions, a stock
ledger attributing every take/restock/adjust to a badge-resolved
employee, a touch kiosk (scan bin, scan badge, keypad quantity) with a
deliberately open decrement-only take endpoint, 1x0.5in CODE128 bin
labels, low-stock email alerts to selected users, roles, or addresses,
and stock/consumption/by-person reports with a cache-vs-ledger
reconcile. Ships disabled; enable per site. Contract 0.13.0 adds the
mailer and the User/Role models to the plugin surface.

plugins/printedparts/tests/test_plugin.py

@@ -0,0 +1,30 @@
+"""Printedparts plugin smoke tests.
+
+Asserts the plugin loads cleanly and satisfies the framework contract.
+Replace and extend with domain tests as you build the plugin out.
+"""
+
+from plugins.printedparts.plugin import PrintedpartsPlugin
+
+
+def test_printedparts_plugin_meta_is_valid():
+    """PrintedpartsPlugin.meta returns a PluginMeta with the expected name."""
+    plugin = PrintedpartsPlugin()
+    assert plugin.meta.name == 'printedparts'
+    assert plugin.meta.api_prefix == '/api/printedparts'
+
+
+def test_printedparts_plugin_get_blueprint_returns_blueprint():
+    """get_blueprint returns a Flask Blueprint, not None."""
+    from flask import Blueprint
+    plugin = PrintedpartsPlugin()
+    assert isinstance(plugin.get_blueprint(), Blueprint)
+
+
+def test_printedparts_plugin_get_models_returns_a_model():
+    """get_models returns a list with at least one SQLAlchemy model."""
+    plugin = PrintedpartsPlugin()
+    models = plugin.get_models()
+    assert len(models) >= 1
+    for model in models:
+        assert hasattr(model, '__tablename__')