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/src/deployment/bootstrap-silo.ts

@@ -250,6 +250,7 @@ async function initializeSilo(
       data: {
         organizationId: input.organization.id,
         name: "Inbox",
+        kind: "SYSTEM_INBOX",
         sortKey: "000000",
       },
     });

hub/src/projectOnboarding.ts

@@ -558,6 +558,26 @@ async function ensureInboxFolder(prisma: Prisma.TransactionClient, organizationI
     select: { id: true },
   });
   if (existing !== null) return existing;
+
+  // Bootstrap once created a root "Inbox" without kind=SYSTEM_INBOX. Sibling-name
+  // uniqueness then makes a second create fail. Recover by promoting that row.
+  const legacyRootInbox = await prisma.folder.findFirst({
+    where: {
+      organizationId,
+      parentId: null,
+      name: "Inbox",
+      archivedAt: null,
+    },
+    select: { id: true },
+  });
+  if (legacyRootInbox !== null) {
+    return prisma.folder.update({
+      where: { id: legacyRootInbox.id },
+      data: { kind: "SYSTEM_INBOX" },
+      select: { id: true },
+    });
+  }
+
   return prisma.folder.create({
     data: { organizationId, name: "Inbox", kind: "SYSTEM_INBOX", sortKey: "000000" },
     select: { id: true },