printedparts stage 1: scaffold, no AssetType, manifest per spec

flask plugin new output, minus the scaffold's AssetType seeding:
printed parts are quantity-based consumables, not ADR-001 assets.
on_install seeds the three plugin settings instead. Manifest pins
core >=0.11.0, depends on employees (badge name resolution), ships
disabled until a site opts in.

plugins/printedparts/plugin.py

@@ -0,0 +1,72 @@
+"""Printedparts plugin main class.
+
+3D-printed parts inventory + kiosk checkout. Quantity-based consumables:
+one row is a KIND of part with a count, not an individually tracked asset,
+so unlike most plugins this one seeds NO AssetType (ADR-001 assets are
+one-row-per-physical-thing). See docs/proposals/printedparts-plugin.md.
+"""
+
+import json
+import logging
+from pathlib import Path
+from typing import List, Optional, Type
+
+from flask import Flask, Blueprint
+
+from shopdb.plugins.base import BasePlugin, PluginMeta
+from shopdb.api import db, Setting
+
+from .models import Printedparts
+from .api import printedparts_bp
+
+logger = logging.getLogger(__name__)
+
+
+class PrintedpartsPlugin(BasePlugin):
+    """3D-printed parts inventory + kiosk checkout."""
+
+    def __init__(self):
+        manifest_path = Path(__file__).parent / 'manifest.json'
+        with open(manifest_path) as f:
+            self._manifest = json.load(f)
+
+    @property
+    def meta(self) -> PluginMeta:
+        return PluginMeta(
+            name=self._manifest['name'],
+            version=self._manifest['version'],
+            description=self._manifest['description'],
+            author=self._manifest.get('author', ''),
+            dependencies=self._manifest.get('dependencies', []),
+            core_version=self._manifest.get('core_version', '>=0.1.0'),
+            api_prefix=self._manifest.get('api_prefix'),
+        )
+
+    def get_blueprint(self) -> Optional[Blueprint]:
+        return printedparts_bp
+
+    def get_models(self) -> List[Type]:
+        return [Printedparts]
+
+    def init_app(self, app: Flask, db_instance) -> None:
+        logger.info(f'Printedparts plugin initialized (v{self.meta.version})')
+
+    def on_install(self, app: Flask) -> None:
+        with app.app_context():
+            self._seed_settings()
+            logger.info('Printedparts plugin installed')
+
+    def _seed_settings(self) -> None:
+        defaults = [
+            ('printedparts_code_prefix', '3DP', 'string',
+             'Prefix for generated item codes'),
+            ('printedparts_default_threshold', '5', 'integer',
+             'Default low-stock threshold for new items'),
+            ('printedparts_unknown_badge', 'deny', 'string',
+             'Kiosk policy when a badge resolves to no employee: allow or deny'),
+        ]
+        for key, value, valuetype, description in defaults:
+            if Setting.get(key) is None:
+                Setting.set(key, value, valuetype=valuetype,
+                            category='printedparts', description=description)
+        db.session.commit()