Migrate the API to native ESM and vitest; pin Node 26

Prep PR for the admin auth module (docs/plan-admin-auth.md step 1).
better-auth 1.7 ships ESM only, so the API moves off CommonJS:

- "type": "module", module nodenext, target ES2024, .js suffixes on all
  relative imports, require('mariadb'|'cors') replaced by imports, and
  export= packages (winston, app-root-path, bcrypt) consumed via default
  imports. The logger now uses appRoot.path explicitly.
- TypeScript 5.9, @types/node 26, tslint removed. Node 26 pinned via
  engines and .nvmrc (Plesk runs 26).
- Jest 28 + ts-jest replaced by vitest 5. Eight test files depend on
  hoisted module mocks with static imports and resetModules + require,
  which Jest's ESM mode does not support; vitest keeps them nearly
  verbatim. Coverage via @vitest/coverage-v8 (lcov), Sonar generic report
  via vitest-sonar-reporter, so sonar-project.properties is unchanged.
  vitest.config.ts sets FEEDBACK_IP_SALT so the suite passes without a
  local .env.
- dotenv 8 -> 16 and axios 0.24 -> 1.x: their old typings are not
  resolvable under nodenext.
- autoCommit: false dropped from the pool configs; it is not a mariadb
  connector option and was silently ignored.

tsc clean, 96/96 tests green, compiled app boots and serves /, /docs and
CORS under Node ESM.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/models/feedback/admin/admin.interface.ts

@@ -81,7 +81,7 @@
  *           type: boolean
  */
 
-import {QuestionType, Song} from '../feedback.interface';
+import {QuestionType, Song} from '../feedback.interface.js';
 
 export interface EventAdminSummary {
 	eventId: number;

src/models/feedback/admin/admin.router.ts

@@ -2,13 +2,13 @@
  * Required External Modules and Interfaces
  */
 import express, {Request, Response} from 'express';
-import {requireAdminAuth} from '../feedback.auth';
-import {sendServerError} from '../feedback.errors';
-import {eventsAdminRouter} from './events.admin.router';
-import {songsAdminRouter} from './songs.admin.router';
-import {questionsAdminRouter} from './questions.admin.router';
-import {reportsAdminRouter} from './reports.admin.router';
-import * as ReportsAdminService from './reports.admin.service';
+import {requireAdminAuth} from '../feedback.auth.js';
+import {sendServerError} from '../feedback.errors.js';
+import {eventsAdminRouter} from './events.admin.router.js';
+import {songsAdminRouter} from './songs.admin.router.js';
+import {questionsAdminRouter} from './questions.admin.router.js';
+import {reportsAdminRouter} from './reports.admin.router.js';
+import * as ReportsAdminService from './reports.admin.service.js';
 
 /**
  * Router Definition

src/models/feedback/admin/csv.service.ts

@@ -1,5 +1,5 @@
-import {NachklangFeedbackDB} from '../Feedback.db';
-import {formatDatetime} from '../feedback.dates';
+import {NachklangFeedbackDB} from '../Feedback.db.js';
+import {formatDatetime} from '../feedback.dates.js';
 
 const CSV_SEPARATOR = ';';
 const UTF8_BOM = '';

src/models/feedback/admin/events.admin.router.ts

@@ -2,9 +2,9 @@
  * Required External Modules and Interfaces
  */
 import express, {Request, Response} from 'express';
-import * as EventsAdminService from './events.admin.service';
-import * as SongsAdminService from './songs.admin.service';
-import {sendServerError} from '../feedback.errors';
+import * as EventsAdminService from './events.admin.service.js';
+import * as SongsAdminService from './songs.admin.service.js';
+import {sendServerError} from '../feedback.errors.js';
 
 /**
  * Router Definition

src/models/feedback/admin/events.admin.service.ts

@@ -1,7 +1,7 @@
-import {NachklangFeedbackDB} from '../Feedback.db';
-import {Song} from '../feedback.interface';
-import {CreateEventInput, EventAdminDetail, EventAdminQuestionAssignment, EventAdminSummary, UpdateEventInput} from './admin.interface';
-import {formatDatetime} from '../feedback.dates';
+import {NachklangFeedbackDB} from '../Feedback.db.js';
+import {Song} from '../feedback.interface.js';
+import {CreateEventInput, EventAdminDetail, EventAdminQuestionAssignment, EventAdminSummary, UpdateEventInput} from './admin.interface.js';
+import {formatDatetime} from '../feedback.dates.js';
 
 const UMLAUT_MAP: Record<string, string> = {
 	'ä': 'ae', 'ö': 'oe', 'ü': 'ue', 'ß': 'ss',

src/models/feedback/admin/questions.admin.router.ts

@@ -2,8 +2,8 @@
  * Required External Modules and Interfaces
  */
 import express, {Request, Response} from 'express';
-import * as QuestionsAdminService from './questions.admin.service';
-import {sendServerError} from '../feedback.errors';
+import * as QuestionsAdminService from './questions.admin.service.js';
+import {sendServerError} from '../feedback.errors.js';
 
 /**
  * Router Definition

src/models/feedback/admin/questions.admin.service.ts

@@ -1,6 +1,6 @@
-import {NachklangFeedbackDB} from '../Feedback.db';
-import {QuestionType} from '../feedback.interface';
-import {AdminQuestion} from './admin.interface';
+import {NachklangFeedbackDB} from '../Feedback.db.js';
+import {QuestionType} from '../feedback.interface.js';
+import {AdminQuestion} from './admin.interface.js';
 
 const mapRow = (row: any): AdminQuestion => ({
 	questionId: row.question_id,

src/models/feedback/admin/reports.admin.interface.ts

@@ -1,4 +1,4 @@
-import {QuestionType} from '../feedback.interface';
+import {QuestionType} from '../feedback.interface.js';
 
 export interface SongPickResult {
 	songId: number;

src/models/feedback/admin/reports.admin.router.ts

@@ -2,10 +2,10 @@
  * Required External Modules and Interfaces
  */
 import express, {Request, Response} from 'express';
-import * as ReportsAdminService from './reports.admin.service';
-import * as CsvService from './csv.service';
-import * as EventsAdminService from './events.admin.service';
-import {sendServerError} from '../feedback.errors';
+import * as ReportsAdminService from './reports.admin.service.js';
+import * as CsvService from './csv.service.js';
+import * as EventsAdminService from './events.admin.service.js';
+import {sendServerError} from '../feedback.errors.js';
 
 /**
  * Router Definition

src/models/feedback/admin/reports.admin.service.ts

@@ -1,7 +1,7 @@
-import {NachklangFeedbackDB} from '../Feedback.db';
+import {NachklangFeedbackDB} from '../Feedback.db.js';
 import {
 	AnswerRow, EventReport, FreeTextReport, SongPickReport, SongRatingReport
-} from './reports.admin.interface';
+} from './reports.admin.interface.js';
 
 const FREE_TEXT_CAP = 500;
 

src/models/feedback/admin/songs.admin.router.ts

@@ -2,8 +2,8 @@
  * Required External Modules and Interfaces
  */
 import express, {Request, Response} from 'express';
-import * as SongsAdminService from './songs.admin.service';
-import {sendServerError} from '../feedback.errors';
+import * as SongsAdminService from './songs.admin.service.js';
+import {sendServerError} from '../feedback.errors.js';
 
 /**
  * Router Definition

src/models/feedback/admin/songs.admin.service.ts

@@ -1,4 +1,4 @@
-import {NachklangFeedbackDB} from '../Feedback.db';
+import {NachklangFeedbackDB} from '../Feedback.db.js';
 
 export const addSong = async (eventId: number, title: string, composer: string | null): Promise<number> => {
 	let conn = await NachklangFeedbackDB.getConnection();