Redesign login UI, add theme toggle, refactor user update

- Redesigned login page with two-panel layout and branding
- Added HexaDistro logo and theme toggle to sidebar/header
- Refactored user update: roles via update endpoint, removed assignRole API/controller
- Extended UpdateUserRequest for username, role, password changes
- UserService.UpdateAsync syncs changes with AuthHex, with rollback
- Stock balances client dedupes by itemId-locationId
- Middleware matcher excludes static assets from auth checks
- Improved localStorage clearing for user context
- Added lucide-react for icons
- Minor UI/code cleanups for consistency and UX

distribution_fe/components/layout/theme-toggle.tsx

@@ -0,0 +1,24 @@
+'use client'
+
+import { useEffect, useState } from 'react'
+import { useTheme } from 'next-themes'
+import { Sun, Moon } from 'lucide-react'
+import { Button } from '@/components/ui/button'
+
+export function ThemeToggle() {
+  const { resolvedTheme, setTheme } = useTheme()
+  const [mounted, setMounted] = useState(false)
+  useEffect(() => setMounted(true), [])
+
+  return (
+    <Button
+      variant="ghost"
+      size="icon"
+      onClick={() => setTheme(resolvedTheme === 'dark' ? 'light' : 'dark')}
+      className="h-8 w-8 text-muted-foreground hover:text-foreground"
+      aria-label="Toggle theme"
+    >
+      {mounted && (resolvedTheme === 'dark' ? <Sun size={16} /> : <Moon size={16} />)}
+    </Button>
+  )
+}