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).

frontend/src/views/AppLayout.vue

@@ -101,7 +101,7 @@ import ToastHost from '../components/ToastHost.vue'
 import {
   Sun, Moon, LayoutDashboard, Calendar, Map, Cog, Monitor,
   Printer, Globe, Usb, AppWindow, BookOpen, BarChart3, Bell, Image, ShieldCheck, Ruler,
-  KeyRound, LogOut
+  Box, KeyRound, LogOut
 } from 'lucide-vue-next'
 import { useAuthStore } from '../stores/auth'
 import { currentTheme, toggleTheme } from '../stores/theme'
@@ -147,6 +147,7 @@ const iconMap = {
   'image': Image,
   'shield': ShieldCheck,
   'ruler': Ruler,
+  'box': Box,
 }
 
 // Default navigation (used as fallback if API fails)