chore: remove IS_AI_ENABLED feature flag (#19916)

## Summary
- AI is now GA, so the public/lab `IS_AI_ENABLED` flag is removed from
`FeatureFlagKey`, the public flag catalog, and the dev seeder.
- Drops every backend `@RequireFeatureFlag(IS_AI_ENABLED)` guard (agent,
agent chat, chat subscription, role-to-agent assignment, workflow AI
step creation) and the now-unused `FeatureFlagModule`/`FeatureFlagGuard`
wiring in the AI and workflow modules.
- Removes frontend gating from settings nav, role
permissions/assignment/applicability, command menu hotkeys, side panel,
mobile/drawer nav, and the agent chat provider so AI UI is always on.
Tests and generated GraphQL/SDK schemas updated accordingly.

## Test plan
- [x] `npx nx typecheck twenty-shared`
- [x] `npx nx typecheck twenty-server`
- [x] `npx nx typecheck twenty-front`
- [x] `npx nx lint:diff-with-main twenty-server`
- [x] `npx nx lint:diff-with-main twenty-front`
- [x] `npx jest --config=packages/twenty-server/jest.config.mjs
feature-flag`
- [x] `npx jest --config=packages/twenty-server/jest.config.mjs
workspace-entity-manager`
- [ ] Manual smoke test: AI features still accessible without any flag
row in `featureFlag`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

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

packages/twenty-front/src/modules/settings/hooks/useSettingsNavigationItems.tsx

@@ -12,7 +12,6 @@ import {
   type NavigationDrawerItemModifier,
 } from '@/ui/navigation/navigation-drawer/components/NavigationDrawerItem';
 import { useAtomStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomStateValue';
-import { useIsFeatureEnabled } from '@/workspace/hooks/useIsFeatureEnabled';
 import { t } from '@lingui/core/macro';
 import { isNonEmptyString } from '@sniptt/guards';
 import {
@@ -39,10 +38,7 @@ import {
   IconUsers,
   IconWorld,
 } from 'twenty-ui/display';
-import {
-  FeatureFlagKey,
-  PermissionFlagType,
-} from '~/generated-metadata/graphql';
+import { PermissionFlagType } from '~/generated-metadata/graphql';
 
 export type SettingsNavigationSection = {
   label: string;
@@ -74,7 +70,6 @@ const useSettingsNavigationItems = (): SettingsNavigationSection[] => {
   const isAdminEnabled =
     (currentUser?.canImpersonate || currentUser?.canAccessFullAdminPanel) ??
     false;
-  const isAiEnabled = useIsFeatureEnabled(FeatureFlagKey.IS_AI_ENABLED);
   const isSupportChatConfigured =
     supportChat?.supportDriver === 'FRONT' &&
     isNonEmptyString(supportChat.supportFrontChatId);
@@ -182,8 +177,7 @@ const useSettingsNavigationItems = (): SettingsNavigationSection[] => {
           label: t`AI`,
           path: SettingsPath.AI,
           Icon: IconSparkles,
-          isHidden:
-            !isAiEnabled || !permissionMap[PermissionFlagType.WORKSPACE],
+          isHidden: !permissionMap[PermissionFlagType.WORKSPACE],
           modifier: 'new',
         },
         {