fix(hub): mark bootstrap Inbox as SYSTEM_INBOX

Alpha silo bootstrap created the root Inbox without kind=SYSTEM_INBOX, so
Feishu card project creation tried to insert a second Inbox and hit the
sibling-name unique index. Tag the bootstrap folder correctly and promote
any legacy root Inbox on ensure.

hub/test/integration/silo-bootstrap.test.ts

@@ -62,6 +62,11 @@ describe("Alpha Silo bootstrap", () => {
       { roleId: "draft", label: "草稿", isDefault: true },
       { roleId: "review", label: "审校", isDefault: false },
     ]);
+    await expect(prisma.folder.findMany({
+      where: { organizationId: "org_alpha", archivedAt: null },
+      select: { name: true, kind: true, parentId: true },
+    })).resolves.toEqual([{ name: "Inbox", kind: "SYSTEM_INBOX", parentId: null }]);
+
 
     const persisted = JSON.stringify({
       feishu: await prisma.feishuApplicationCredentialVersion.findMany(),