printedparts stage 3: read API + list page (first visible win)

GET /items (paginated, search across code/name/description/bin,
lowstock filter) and GET /items/<id> with recent transactions, both
open reads. printedpartsApi client, router file repointed at the
renamed views, PrintedItemsList with image thumbs and a red/green
quantity badge against the per-item threshold. Nav entry '3D Parts'
with a new 'box' Lucide icon mapping (the sidebar renders nothing for
unknown icon names - lab gotcha).

plugins/printedparts/plugin.py

@@ -51,6 +51,16 @@ class PrintedpartsPlugin(BasePlugin):
     def init_app(self, app: Flask, db_instance) -> None:
         logger.info(f'Printedparts plugin initialized (v{self.meta.version})')
 
+    def get_navigation_items(self) -> List[dict]:
+        return [
+            {
+                'name': '3D Parts',
+                'icon': 'box',
+                'route': '/printedparts',
+                'position': 46,
+            },
+        ]
+
     def on_install(self, app: Flask) -> None:
         with app.app_context():
             self._seed_settings()