fix(web): unpair soft-archives groups instead of DELETE — same FK abort

Web error log showed unpairAccountAction failing with the same FK
violation as group-sync: deleting whatsapp_groups rows that had been
used in reminders blew up reminder_targets_group_id_whatsapp_groups_id_fk
and aborted the unpair.

Switch to UPDATE … SET is_archived=true. The bot's group-sync upsert
already flips is_archived back to false on a re-pair (added in the
group-sync companion fix in the previous commit), so behaviour is
end-to-end equivalent to the old delete + repopulate path without
the FK fragility.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/actions/accounts.ts

@@ -172,8 +172,16 @@ export async function unpairAccountAction(formData: FormData): Promise<void> {
     .update(whatsappAccounts)
     .set({ status: "unpaired", phoneNumber: null })
     .where(eq(whatsappAccounts.id, accountId));
-  // Wipe synced groups too — they belong to a different WA login now.
-  await db.delete(whatsappGroups).where(eq(whatsappGroups.accountId, accountId));
+  // Soft-archive synced groups instead of DELETEing. Hard delete
+  // failed with "violates foreign key constraint
+  // reminder_targets_group_id_whatsapp_groups_id_fk" whenever any
+  // group had ever been used in a reminder, which aborted the
+  // unpair. Archived groups vanish from the picker; a re-pair flips
+  // them back via the on-conflict upsert in syncGroupsForAccount.
+  await db
+    .update(whatsappGroups)
+    .set({ isArchived: true })
+    .where(eq(whatsappGroups.accountId, accountId));
   revalidatePath("/accounts");
   revalidatePath(`/accounts/${accountId}`);
   // eslint-disable-next-line @typescript-eslint/no-explicit-any