Add USB, Notifications, Network plugins and reusable EmployeeSearch component

New Plugins:
- USB plugin: Device checkout/checkin with employee lookup, checkout history
- Notifications plugin: Announcements with types, scheduling, shopfloor display
- Network plugin: Network device management with subnets and VLANs
- Equipment and Computers plugins: Asset type separation

Frontend:
- EmployeeSearch component: Reusable employee lookup with autocomplete
- USB views: List, detail, checkout/checkin modals
- Notifications views: List, form with recognition mode
- Network views: Device list, detail, form
- Calendar view with FullCalendar integration
- Shopfloor and TV dashboard views
- Reports index page
- Map editor for asset positioning
- Light/dark mode fixes for map tooltips

Backend:
- Employee search API with external lookup service
- Collector API for PowerShell data collection
- Reports API endpoints
- Slides API for TV dashboard
- Fixed AppVersion model (removed BaseModel inheritance)
- Added checkout_name column to usbcheckouts table

Styling:
- Unified detail page styles
- Improved pagination (page numbers instead of prev/next)
- Dark/light mode theme improvements

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/stores/theme.js

@@ -0,0 +1,39 @@
+import { ref, watch } from 'vue'
+
+const STORAGE_KEY = 'shopdb-theme'
+
+// Get initial theme from localStorage or system preference
+function getInitialTheme() {
+  const stored = localStorage.getItem(STORAGE_KEY)
+  if (stored) return stored
+
+  // Fall back to system preference
+  if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+    return 'dark'
+  }
+  return 'light'
+}
+
+export const currentTheme = ref(getInitialTheme())
+
+// Apply theme to document
+function applyTheme(theme) {
+  document.documentElement.setAttribute('data-theme', theme)
+  localStorage.setItem(STORAGE_KEY, theme)
+}
+
+// Initialize on load
+applyTheme(currentTheme.value)
+
+// Watch for changes
+watch(currentTheme, (newTheme) => {
+  applyTheme(newTheme)
+})
+
+export function toggleTheme() {
+  currentTheme.value = currentTheme.value === 'dark' ? 'light' : 'dark'
+}
+
+export function setTheme(theme) {
+  currentTheme.value = theme
+}