Moved redirects modules to backend

refs https://linear.app/tryghost/issue/CORE-35/refactor-route-and-redirect-settings

- These modules should be colocated on the backend side as the frontend should know nothing about "where the config comes from" in terms of file system or any other source.

core/server/api/canary/redirects.js

@@ -1,7 +1,7 @@
 const path = require('path');
 
 const web = require('../../web');
-const redirects = require('../../../frontend/services/redirects');
+const redirects = require('../../services/redirects');
 
 module.exports = {
     docName: 'redirects',

core/server/api/v2/redirects.js

@@ -1,5 +1,5 @@
 const web = require('../../web');
-const redirects = require('../../../frontend/services/redirects');
+const redirects = require('../../services/redirects');
 
 module.exports = {
     docName: 'redirects',

core/server/api/v3/redirects.js

@@ -1,7 +1,7 @@
 const path = require('path');
 
 const web = require('../../web');
-const redirects = require('../../../frontend/services/redirects');
+const redirects = require('../../services/redirects');
 
 module.exports = {
     docName: 'redirects',

core/server/web/shared/middlewares/custom-redirects.js

@@ -7,7 +7,7 @@ const urlUtils = require('../../../../shared/url-utils');
 const errors = require('@tryghost/errors');
 const i18n = require('../../../../shared/i18n');
 const logging = require('@tryghost/logging');
-const redirectsService = require('../../../../frontend/services/redirects');
+const redirectsService = require('../../../services/redirects');
 
 const _private = {};