Security-Hardening Runde 3: JWT, trust-proxy, weitere IDORs, Attachment-Härtung

- JWT-Algorithmus fest auf HS256 (Defense-in-Depth gegen alg-confusion)
- app.set('trust proxy', 1) – Rate-Limiter wirkt jetzt auch hinter Reverse-Proxy
- IDOR-Fix: Invoice-ECD-Endpoints + PDF-Template-Generierung (canAccessContract/ECD)
- Email-Anhang-Download: Content-Type-Safelist, SVG nie inline, nosniff, Filename-CRLF-Sanitize
- Provider/Tariff-GET-Routen: requirePermission('providers:read') (Portal-Kunden raus)
- SMTP-Header-Injection zentral in sendEmail blockiert (schützt alle Caller)
- bcrypt-Cost 10 → 12 (OWASP 2026)

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

backend/src/controllers/pdfTemplate.controller.ts

@@ -2,6 +2,7 @@ import { Response } from 'express';
 import { AuthRequest } from '../types/index.js';
 import * as pdfTemplateService from '../services/pdfTemplate.service.js';
 import { logChange } from '../services/audit.service.js';
+import { canAccessContract } from '../utils/accessControl.js';
 
 export async function getTemplates(req: AuthRequest, res: Response) {
   try {
@@ -149,6 +150,7 @@ export async function getRequiredInputs(req: AuthRequest, res: Response) {
   try {
     const templateId = parseInt(req.params.id);
     const contractId = parseInt(req.params.contractId);
+    if (!(await canAccessContract(req, res, contractId))) return;
     const inputs = await pdfTemplateService.getRequiredInputs(templateId, contractId);
     res.json({ success: true, data: inputs });
   } catch (error) {
@@ -160,6 +162,7 @@ export async function generatePdf(req: AuthRequest, res: Response) {
   try {
     const templateId = parseInt(req.params.id);
     const contractId = parseInt(req.params.contractId);
+    if (!(await canAccessContract(req, res, contractId))) return;
 
     // Extras aus Body (POST) oder Query-Parametern (GET)
     const stressfreiEmailId = req.body?.stressfreiEmailId || req.query.stressfreiEmailId;