feat(auth): complete sqlite auth and client invitations

app/api/portal-invitations/accept/route.ts

@@ -0,0 +1,29 @@
+import { NextResponse } from "next/server";
+import {
+  acceptPortalInvitation,
+  PortalInvitationError,
+} from "@/server/auth/invitations";
+
+export async function POST(request: Request) {
+  try {
+    const body = await request.json();
+    await acceptPortalInvitation({
+      token: body.token,
+      displayName: body.displayName,
+      password: body.password,
+    });
+
+    return NextResponse.json({ success: true }, { status: 201 });
+  } catch (error) {
+    if (error instanceof SyntaxError) {
+      return NextResponse.json({ error: "Geçersiz JSON gövdesi." }, { status: 400 });
+    }
+    if (error instanceof PortalInvitationError) {
+      const status = error.code === "INVALID_INPUT" ? 400 : 409;
+      return NextResponse.json({ error: error.message, code: error.code }, { status });
+    }
+
+    console.error("Portal invitation accept failed", error);
+    return NextResponse.json({ error: "Portal hesabı oluşturulamadı." }, { status: 500 });
+  }
+}