Policies: let team leaders configure policies in the UI (#6634)

Frontend follow-up to #6632 (team-scoped policies, editing gated to team
leaders on the backend). Brings the UI's edit gate in line.

## Problem
The policy config UI gated editing to `config.isAdmin`. On SaaS, org
users are never the single global admin, so **no one could open the
policy editor** — the same lockout #6632 fixed on the backend.

## Fix
`usePolicies` now allows a **team leader** to configure, falling back to
a global admin self-hosted:

```ts
canConfigure =
  config != null && (!config.enableLogin || isTeamLeader || config.isAdmin === true);
```

- SaaS → `isTeamLeader` (from `useSaaSTeam()`) — team leaders can
configure; members get the read-only surface.
- Self-hosted → `config.isAdmin` (the core `useSaaSTeam` stub returns
`false`, so admins aren't locked out).
- Login disabled (single-user) → always allowed.
- The `config != null` guard keeps the gate closed until app-config
resolves, so edit controls never flash for users who can't use them.

The two locked-policy banners now read "Contact a team leader to change
this policy" (updated in the `t()` defaults and the `en-GB`
translations).

## Verification
- Typecheck clean (proprietary + saas); eslint clean.
- Tests pass: `usePolicies`, `PoliciesSidebar`.

frontend/editor/public/locales/en-GB/translation.toml

@@ -5869,7 +5869,7 @@ security = "Security"
 [policies.detail]
 editSettings = "Edit Settings"
 enforces = "Enforces"
-managedByOrg = "Managed by your organization. Contact an admin to change this policy."
+managedByOrg = "Managed by your organization. Contact a team leader to change this policy."
 noActivityDescription = "Documents will appear here once this policy runs."
 noActivityTitle = "No activity yet"
 onEveryUpload = "On every upload"
@@ -5931,7 +5931,7 @@ filenamePrefix = "Prefix"
 filenameSuffix = "Suffix"
 filenameTextAria = "Filename text"
 filenameTextPlaceholder = "Text to add (optional)"
-lockedDescription = "Contact an admin to change this policy."
+lockedDescription = "Contact a team leader to change this policy."
 lockedTitle = "Managed by your organization"
 maxRetriesLabel = "Max retries"
 noToolsError = "Add at least one configured tool to the workflow first."

frontend/editor/src/proprietary/components/policies/PolicyDetailPanel.tsx

@@ -279,7 +279,7 @@ export function PolicyDetailPanel({
             icon={<LockIcon sx={{ fontSize: "1rem" }} />}
             description={t(
               "policies.detail.managedByOrg",
-              "Managed by your organization. Contact an admin to change this policy.",
+              "Managed by your organization. Contact a team leader to change this policy.",
             )}
           />
         )}

frontend/editor/src/proprietary/components/policies/PolicySetupWizard.tsx

@@ -179,7 +179,7 @@ export function PolicySetupWizard({
             )}
             description={t(
               "policies.wizard.lockedDescription",
-              "Contact an admin to change this policy.",
+              "Contact a team leader to change this policy.",
             )}
           />
         </div>

frontend/editor/src/proprietary/hooks/usePolicies.ts

@@ -8,6 +8,7 @@
 
 import { useState, useEffect, useCallback } from "react";
 import { useAppConfig } from "@app/contexts/AppConfigContext";
+import { useSaaSTeam } from "@app/contexts/SaaSTeamContext";
 import {
   loadPolicies,
   onPoliciesChange,
@@ -65,6 +66,7 @@ function toStoreRequest(
 export function usePolicies() {
   const [policies, setPolicies] = useState<PoliciesByCategory>(loadPolicies);
   const { config } = useAppConfig();
+  const { isTeamLeader } = useSaaSTeam();
 
   useEffect(() => onPoliciesChange(() => setPolicies(loadPolicies())), []);
 
@@ -293,17 +295,13 @@ export function usePolicies() {
     return folder.id;
   }, []);
 
-  // Editing/creating policies is admin-only, mirroring the backend's enforcement
-  // on the save/delete endpoints. On single-user deployments (login disabled)
-  // there's no admin concept, so the local operator can always configure. When
-  // login is enabled, only admins can — non-admins get the read-only surface.
-  // The `config != null` guard keeps the gate CLOSED until app-config resolves:
-  // config is null while loading (and in bare test renders), and a failed/partial
-  // fetch can yield `{ enableLogin: true }` with isAdmin omitted. Without it a
-  // non-admin would briefly see edit controls during load, and an admin would be
-  // wrongly locked out on a transient config-fetch error.
+  // Only a team leader (SaaS) or a global admin (self-hosted) may configure;
+  // everyone else gets the read-only surface. Login disabled (single-user)
+  // always can. Stays closed until config loads, so edit controls never flash
+  // for users who can't use them.
   const canConfigure =
-    config != null && (!config.enableLogin || config.isAdmin === true);
+    config != null &&
+    (!config.enableLogin || isTeamLeader || config.isAdmin === true);
 
   return {
     policies,