fix: rename SettingsPermissionsGuard to SettingsPermissionGuard for consistency (#15712)

## Problem

The ESLint rule `graphql-resolvers-should-be-guarded` introduced in
#15392 was failing on main because the guard `SettingsPermissionsGuard`
had inconsistent naming.

## Root Cause

The guard was named `SettingsPermissionsGuard` (with an 's') which was
inconsistent with other permission guards:
- ✅ `CustomPermissionGuard`  
- ✅ `NoPermissionGuard`
- ✅ `ImpersonatePermissionGuard`
- ❌ `SettingsPermissionsGuard` (inconsistent!)

The ESLint rule checks if guard names end with `PermissionGuard`, but
`SettingsPermissionsGuard` ends with `sGuard`, so it wasn't recognized
as a permission guard.

## Solution

Renamed the guard to be consistent with the naming convention:

1. ✅ Renamed file: `settings-permissions.guard.ts` →
`settings-permission.guard.ts`
2. ✅ Renamed export: `SettingsPermissionsGuard` →
`SettingsPermissionGuard`
3. ✅ Renamed internal class: `SettingsPermissionsMixin` →
`SettingsPermissionMixin`
4. ✅ Updated all 122 references across 44 files in the codebase
5. ✅ Renamed test file: `settings-permissions.guard.spec.ts` →
`settings-permission.guard.spec.ts`

## Testing

- ✅ `npx nx run twenty-server:lint` passes
- ✅ `npx nx run twenty-server:typecheck` passes
- ✅ No references to the old name remain in the codebase
- ✅ All previously failing resolver files now pass ESLint validation

## Related

Fixes issues introduced in #15392

packages/twenty-server/src/engine/core-modules/billing/billing.resolver.ts

@@ -29,7 +29,7 @@ import { AuthUserWorkspaceId } from 'src/engine/decorators/auth/auth-user-worksp
 import { AuthUser } from 'src/engine/decorators/auth/auth-user.decorator';
 import { AuthWorkspace } from 'src/engine/decorators/auth/auth-workspace.decorator';
 import { NoPermissionGuard } from 'src/engine/guards/no-permission.guard';
-import { SettingsPermissionsGuard } from 'src/engine/guards/settings-permissions.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';
 import { PermissionFlagType } from 'src/engine/metadata-modules/permissions/constants/permission-flag-type.constants';
@@ -60,7 +60,7 @@ export class BillingResolver {
   @Query(() => BillingSessionOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async billingPortalSession(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -138,7 +138,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async switchSubscriptionInterval(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -160,7 +160,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async switchBillingPlan(@AuthWorkspace() workspace: WorkspaceEntity) {
     await this.billingSubscriptionService.changePlan(workspace);
@@ -180,7 +180,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async cancelSwitchBillingPlan(@AuthWorkspace() workspace: WorkspaceEntity) {
     await this.billingSubscriptionService.cancelSwitchPlan(workspace);
@@ -200,7 +200,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async cancelSwitchBillingInterval(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -222,7 +222,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async setMeteredSubscriptionPrice(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -256,7 +256,7 @@ export class BillingResolver {
   @Mutation(() => BillingEndTrialPeriodOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async endSubscriptionTrialPeriod(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -267,7 +267,7 @@ export class BillingResolver {
   @Query(() => [BillingMeteredProductUsageOutput])
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async getMeteredProductsUsage(
     @AuthWorkspace() workspace: WorkspaceEntity,
@@ -278,7 +278,7 @@ export class BillingResolver {
   @Mutation(() => BillingUpdateOutput)
   @UseGuards(
     WorkspaceAuthGuard,
-    SettingsPermissionsGuard(PermissionFlagType.BILLING),
+    SettingsPermissionGuard(PermissionFlagType.BILLING),
   )
   async cancelSwitchMeteredPrice(@AuthWorkspace() workspace: WorkspaceEntity) {
     await this.billingSubscriptionService.cancelSwitchMeteredPrice(workspace);