fix(role): rebind API keys + agents before deleting their role (#20935)

## Customer-reported bug

A customer hit this when using the AI chat:

```json
{
  "message": "API key 760d4822-da40-4b3f-9031-40563d7ed6c9 has no role assigned",
  "extensions": {
    "code": "INTERNAL_SERVER_ERROR",
    "userFriendlyMessage": "This API key has no role assigned."
  }
}
```

Their integration authenticates via API key. Somewhere along the way,
the role bound to that API key was deleted, leaving the API key
authenticated but role-less. Any request that hits a permission check
(`getRoleIdForApiKeyId`) blows up.

## Root cause

In `RoleService.deleteManyRoles`, the pre-deletion cleanup
(`assignDefaultRoleToMembersWithRoleToDelete`) only rebinds **user
workspaces** to the workspace default role. API keys and agents pointing
at the role are ignored. Because `RoleTargetEntity.role` declares
`onDelete: 'CASCADE'`, the FK then drops the role_target rows for those
API keys / agents — but the API keys themselves stay in `api_key`, now
orphaned in `apiKeyRoleMap`.

A previous read-side workaround
([2767ddac44](https://github.com/twentyhq/twenty/commit/2767ddac44) —
make the `role` ResolveField nullable) handled the API-key-details page,
but did not address the write paths (`getRoleIdForApiKeyId`).

## Fix

- Rename `assignDefaultRoleToMembersWithRoleToDelete` →
`rebindTargetsOfRoleToDeleteToDefaultRole` and extend it to rebind API
keys (via `ApiKeyRoleService.assignRoleToApiKey`) and agents (via
`AiAgentRoleService.assignRoleToAgent`) in the same step, before the
role is deleted.
- If the workspace default role doesn't satisfy `canBeAssignedToApiKeys`
/ `canBeAssignedToAgents`, the inner `assignRoleTo*` validation throws.
We catch that and rethrow as a `PermissionsException` with a
role-deletion-context message and two new codes —
`ROLE_CANNOT_BE_ASSIGNED_TO_API_KEYS` /
`ROLE_CANNOT_BE_ASSIGNED_TO_AGENTS` — so the admin sees a clear
"reassign these first" prompt rather than a confusing inner error.

## Scope / non-goals

- **Already-orphaned API keys are not auto-healed.** The customer still
needs to reassign a role to their existing orphan API key via the UI
(Settings > API Keys > [the key] > role). A separate cleanup command for
existing orphans is a follow-up.
- I did not investigate *why* the customer's session was authenticated
via API key in the AI chat — that may be their integration setup. Worth
confirming with them separately.

## Test plan

- [ ] Workspace with default role `Admin` (which has
`canBeAssignedToApiKeys: true`): create an API key with a custom role,
delete the custom role → API key is rebound to Admin, requests keep
working.
- [ ] Workspace with default role `Member` (default, has
`canBeAssignedToApiKeys: false`): create an API key with a custom role,
delete the custom role → role deletion fails with the new
`ROLE_CANNOT_BE_ASSIGNED_TO_API_KEYS` error explaining the admin must
reassign first. API key + custom role are both unchanged.
- [ ] Same two scenarios for agents (`canBeAssignedToAgents`).
- [ ] Existing user-workspace rebind behavior is unchanged.
- [ ] Role deletion with no dependent API keys / agents still works.

packages/twenty-front/src/modules/settings/roles/role-settings/components/SettingsRoleSettingsDeleteRoleConfirmationModalSubtitle.tsx

@@ -1,6 +1,6 @@
 import { settingsDraftRoleFamilyState } from '@/settings/roles/states/settingsDraftRoleFamilyState';
 import { useAtomFamilyStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomFamilyStateValue';
-import { t } from '@lingui/core/macro';
+import { plural, t } from '@lingui/core/macro';
 
 type SettingsRoleSettingsDeleteRoleConfirmationModalSubtitleProps = {
   roleId: string;
@@ -14,8 +14,51 @@ export const SettingsRoleSettingsDeleteRoleConfirmationModalSubtitle = ({
     roleId,
   );
   const roleName = settingsDraftRole.label;
+  const memberCount = settingsDraftRole.workspaceMembers.length;
+  const apiKeyCount = settingsDraftRole.apiKeys.length;
+  const agentCount = settingsDraftRole.agents.length;
+
+  const segments: string[] = [];
+
+  if (memberCount > 0) {
+    segments.push(
+      plural(memberCount, {
+        one: `${memberCount} member`,
+        other: `${memberCount} members`,
+      }),
+    );
+  }
+
+  if (apiKeyCount > 0) {
+    segments.push(
+      plural(apiKeyCount, {
+        one: `${apiKeyCount} API key`,
+        other: `${apiKeyCount} API keys`,
+      }),
+    );
+  }
+
+  if (agentCount > 0) {
+    segments.push(
+      plural(agentCount, {
+        one: `${agentCount} agent`,
+        other: `${agentCount} agents`,
+      }),
+    );
+  }
+
+  if (segments.length === 0) {
+    return (
+      <>{t`Confirm deletion of ${roleName} role? This cannot be undone.`}</>
+    );
+  }
+
+  const reassignSubject =
+    segments.length === 1
+      ? segments[0]
+      : `${segments.slice(0, -1).join(', ')} ${t`and`} ${segments.at(-1)}`;
 
   return (
-    <>{t`Confirm deletion of ${roleName} role? This cannot be undone. All members will be reassigned to the default role.`}</>
+    <>{t`Confirm deletion of ${roleName} role? This cannot be undone. ${reassignSubject} will be reassigned to the default role.`}</>
   );
 };