Add dashboard, layout components, and CRM scaffolding

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/layout/header.tsx

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+export function Header({ title }: { title: string }) {
+  return (
+    <header className="h-16 flex items-center justify-between px-6 border-b border-black/10 dark:border-white/10 bg-white dark:bg-neutral-950">
+      <h1 className="text-lg font-semibold">{title}</h1>
+      <div className="flex items-center gap-3">
+        <div className="h-8 w-8 rounded-full bg-neutral-200 dark:bg-neutral-800" />
+      </div>
+    </header>
+  );
+}

src/components/layout/sidebar.tsx

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+"use client";
+
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+import { siteConfig, navItems } from "@/config/site";
+import { cn } from "@/lib/utils";
+
+export function Sidebar() {
+  const pathname = usePathname();
+
+  return (
+    <aside className="hidden md:flex md:w-60 md:flex-col border-r border-black/10 dark:border-white/10 bg-white dark:bg-neutral-950">
+      <div className="h-16 flex items-center px-6 font-semibold text-lg border-b border-black/10 dark:border-white/10">
+        {siteConfig.shortName}
+      </div>
+      <nav className="flex-1 p-3 space-y-1">
+        {navItems.map((item) => {
+          const active =
+            pathname === item.href || pathname.startsWith(item.href + "/");
+          return (
+            <Link
+              key={item.href}
+              href={item.href}
+              className={cn(
+                "block rounded-md px-3 py-2 text-sm font-medium transition-colors",
+                active
+                  ? "bg-neutral-900 text-white dark:bg-white dark:text-neutral-900"
+                  : "text-neutral-600 hover:bg-neutral-100 dark:text-neutral-400 dark:hover:bg-neutral-900"
+              )}
+            >
+              {item.title}
+            </Link>
+          );
+        })}
+      </nav>
+    </aside>
+  );
+}