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/page.tsx

@@ -1,10 +1,11 @@
 import Link from "next/link";
 import { redirect } from "next/navigation";
+import { headers } from "next/headers";
 import { Button } from "~/components/ui/button";
 import { Card, CardContent, CardHeader, CardTitle } from "~/components/ui/card";
 import { Badge } from "~/components/ui/badge";
 import { Logo } from "~/components/ui/logo";
-import { auth } from "~/server/auth";
+import { auth } from "~/lib/auth";
 import {
   ArrowRight,
   Beaker,
@@ -20,7 +21,9 @@ import {
 } from "lucide-react";
 
 export default async function Home() {
-  const session = await auth();
+  const session = await auth.api.getSession({
+    headers: await headers(),
+  });
 
   if (session?.user) {
     redirect("/dashboard");