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-server/src/engine/metadata-modules/role/role.resolver.ts

@@ -8,7 +8,6 @@ import { Args, Mutation, Parent, Query, ResolveField } from '@nestjs/graphql';
 
 import { msg } from '@lingui/core/macro';
 import { PermissionFlagType } from 'twenty-shared/constants';
-import { FeatureFlagKey } from 'twenty-shared/types';
 import { isDefined } from 'twenty-shared/utils';
 
 import { MetadataResolver } from 'src/engine/api/graphql/graphql-config/decorators/metadata-resolver.decorator';
@@ -22,7 +21,6 @@ import { WorkspaceMemberDTO } from 'src/engine/core-modules/user/dtos/workspace-
 import { WorkspaceEntity } from 'src/engine/core-modules/workspace/workspace.entity';
 import { AuthWorkspaceMemberId } from 'src/engine/decorators/auth/auth-workspace-member-id.decorator';
 import { AuthWorkspace } from 'src/engine/decorators/auth/auth-workspace.decorator';
-import { RequireFeatureFlag } from 'src/engine/guards/feature-flag.guard';
 import { SettingsPermissionGuard } from 'src/engine/guards/settings-permission.guard';
 import { UserAuthGuard } from 'src/engine/guards/user-auth.guard';
 import { WorkspaceAuthGuard } from 'src/engine/guards/workspace-auth.guard';
@@ -270,7 +268,6 @@ export class RoleResolver {
   }
 
   @Mutation(() => Boolean)
-  @RequireFeatureFlag(FeatureFlagKey.IS_AI_ENABLED)
   async assignRoleToAgent(
     @Args('agentId', { type: () => UUIDScalarType }) agentId: string,
     @Args('roleId', { type: () => UUIDScalarType }) roleId: string,
@@ -286,7 +283,6 @@ export class RoleResolver {
   }
 
   @Mutation(() => Boolean)
-  @RequireFeatureFlag(FeatureFlagKey.IS_AI_ENABLED)
   async removeRoleFromAgent(
     @Args('agentId', { type: () => UUIDScalarType }) agentId: string,
     @AuthWorkspace() { id: workspaceId }: WorkspaceEntity,