migrate: replace NextAuth.js with Better Auth

- Install better-auth and @better-auth/drizzle-adapter
- Create src/lib/auth.ts with Better Auth configuration using bcrypt
- Update database schema: change auth table IDs from uuid to text
- Update route handler from /api/auth/[...nextauth] to /api/auth/[...all]
- Update tRPC context and middleware for Better Auth session handling
- Update client components to use Better Auth APIs (signIn, signOut)
- Update seed script with text-based IDs and correct account schema
- Fix type errors in wizard components (robotId, optional chaining)
- Fix API paths: api.robots.initialize -> api.robots.plugins.initialize
- Update auth router to use text IDs for Better Auth compatibility

Note: Auth tables were reset - users will need to re-register.

src/app/dashboard/page.tsx

@@ -57,7 +57,7 @@ import { Badge } from "~/components/ui/badge";
 import { ScrollArea } from "~/components/ui/scroll-area";
 import { api } from "~/trpc/react";
 import { useTour } from "~/components/onboarding/TourProvider";
-import { useSession } from "next-auth/react";
+import { useSession } from "~/lib/auth-client";
 
 export default function DashboardPage() {
   const { startTour } = useTour();