feat: user auth, API keys, Stripe billing, and dashboard scoping

- NextAuth v5 credentials auth with registration/login pages
- API key CRUD (create, list, revoke) with secure hashing
- Stripe checkout, webhooks, and customer portal integration
- Rate limiting per subscription tier
- All dashboard API endpoints scoped to authenticated user
- Prisma schema: User, Account, Session, ApiKey, plus Stripe fields
- Auth middleware protecting dashboard and API routes

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-Claude)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

apps/web/src/app/dashboard/layout.tsx

@@ -6,6 +6,7 @@ import { usePathname } from "next/navigation";
 import {
   Activity,
   GitBranch,
+  Key,
   Settings,
   Menu,
   ChevronRight,
@@ -22,6 +23,7 @@ interface NavItem {
 const navItems: NavItem[] = [
   { href: "/dashboard", label: "Traces", icon: Activity },
   { href: "/dashboard/decisions", label: "Decisions", icon: GitBranch },
+  { href: "/dashboard/keys", label: "API Keys", icon: Key },
   { href: "/dashboard/settings", label: "Settings", icon: Settings },
 ];