fix: two polling bugs — correspondent 400 and Agrarmonitor 403

- 400 on Korrespondenten-Sync: getCorrespondentByName was called with
  searchName "(12345)" but checked exact match against full displayName
  "Firma (12345)". Always returned null → duplicate addCorrespondent on
  every run → Paperless 400. Fix: search by displayName directly.

- 403 on Livesearch: cached Agrarmonitor session expired. Fix: detect
  401/403 from connector, call clearClient() to invalidate cache, break
  out of the polling loop so next cron run re-authenticates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

paperless-backend/src/agrarmonitor/agrarmonitor-polling.service.ts

@@ -105,9 +105,8 @@ export class AgrarmonitorPollingService implements OnModuleInit {
       )) {
         try {
           const lieferantennummer = (customer['lieferantennummer'] as string) ?? '';
-          const searchName = `(${lieferantennummer})`;
           const displayName = this.buildCustomerName(customer, lieferantennummer);
-          const existing = await this.paperlessService.getCorrespondentByName(searchName);
+          const existing = await this.paperlessService.getCorrespondentByName(displayName);
           if (!existing) {
             await this.paperlessService.addCorrespondent({
               name: displayName,
@@ -153,6 +152,14 @@ export class AgrarmonitorPollingService implements OnModuleInit {
         try {
           amResults = await amClient.eingangsrechnungenLivesearch(interneBelegnummer);
         } catch (err: unknown) {
+          const status = (err as any)?.response?.status;
+          if (status === 401 || status === 403) {
+            this.agrarmonitorService.clearClient();
+            const msg = `Session abgelaufen (${status}) — Polling abgebrochen, nächster Lauf meldet sich neu an`;
+            this.logger.warn(msg);
+            result.errors.push(msg);
+            break;
+          }
           const msg = `${interneBelegnummer}: Livesearch-Fehler`;
           this.logger.error(`${msg}: ${err instanceof Error ? err.message : err}`);
           result.errors.push(msg);

paperless-backend/src/agrarmonitor/agrarmonitor.service.ts

@@ -56,6 +56,10 @@ export class AgrarmonitorService {
     return this.client;
   }
 
+  clearClient(): void {
+    this.client = null;
+  }
+
   async getStatus(): Promise<AgrarmonitorStatusDto> {
     try {
       const client = await this.getClient();