feat: Phase 0-2 complete — auth, machines, equipment parts with full CRUD

Multi-tenant factory inspection system (SpiFox, Enkid, Alpet):
- FastAPI backend with JWT auth, PostgreSQL (asyncpg)
- Next.js 16 frontend with App Router, SWR data fetching
- Machines CRUD with equipment parts management
- Part lifecycle tracking (hours/count/date) with counters
- Partial unique index for soft-delete support
- 24 pytest tests passing, E2E verified

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

dashboard/components/AuthGuard.tsx

@@ -0,0 +1,43 @@
+'use client';
+
+import { useEffect } from 'react';
+import { useRouter, usePathname } from 'next/navigation';
+import { useAuth } from '@/lib/auth-context';
+
+const PUBLIC_PATHS = ['/login'];
+
+export function AuthGuard({ children }: { children: React.ReactNode }) {
+  const { isAuthenticated, isLoading } = useAuth();
+  const router = useRouter();
+  const pathname = usePathname();
+
+  const isPublicPath = PUBLIC_PATHS.includes(pathname);
+
+  useEffect(() => {
+    if (isLoading) return;
+
+    if (!isAuthenticated && !isPublicPath) {
+      router.push('/login');
+    } else if (isAuthenticated && isPublicPath) {
+      router.push('/');
+    }
+  }, [isAuthenticated, isLoading, isPublicPath, router]);
+
+  if (isLoading) {
+    return (
+      <div className="auth-loading">
+        <span className="material-symbols-outlined spinning">progress_activity</span>
+      </div>
+    );
+  }
+
+  if (!isAuthenticated && !isPublicPath) {
+    return null;
+  }
+
+  if (isAuthenticated && isPublicPath) {
+    return null;
+  }
+
+  return <>{children}</>;
+}