fix(dkv): correct invoice date extraction; add Exchange IsRead filter + mark-as-read

Date fix: previous regex matched payment-due date ("10 Tage nach Rechnungsdatum...
10.04.2026") instead of actual Rechnungsdatum. New approach anchors on the
invoice number line (DD/DDDDDDDDD/DDD) and takes the date on the next line,
which is always the actual Rechnungsdatum in DKV PDFs.

Exchange dedup: FindItem now filters IsRead=false (combined with sender filter
via <t:And>), so already-processed emails are skipped automatically.
After downloading attachments, UpdateItem marks the message as read
(using ItemId + ChangeKey from GetItem response), mirroring IMAP \Seen behavior.

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

apps/api/src/dkv/dkv-parser.service.ts

@@ -69,17 +69,15 @@ export class DkvParserService {
     return m ? m[1] : null;
   }
 
-  /** Extract invoice date ("DD.MM.YYYY") appearing near "Rechnungsdatum" in PDF text. */
+  /** Extract invoice date ("DD.MM.YYYY") from PDF text.
+   *  DKV PDFs always print the date on the line immediately after the invoice
+   *  number (DD/DDDDDDDDD/DDD), so we anchor on the number → date pairing.
+   *  The old "Rechnungsdatum[:\s]*date" approach picked up the payment-due date
+   *  ("10 Tage nach Rechnungsdatum. Die Abbuchung erfolgt am: 10.04.2026").
+   */
   private extractRechnungsdatum(text: string): string | null {
-    // "Rechnungsdatum" is followed (within ~200 chars) by a date string
-    const m = text.match(/Rechnungsdatum[:\s\t]*(\d{2}\.\d{2}\.\d{4})/);
-    if (m) return m[1];
-    // Fallback: second line after "Rechnungsdatum:" marker
-    const idx = text.indexOf('Rechnungsdatum');
-    if (idx === -1) return null;
-    const after = text.slice(idx, idx + 200);
-    const dm = after.match(/(\d{2}\.\d{2}\.\d{4})/);
-    return dm ? dm[1] : null;
+    const m = text.match(/\d{2}\/\d{9}\/\d{3}\s+(\d{2}\.\d{2}\.\d{4})/);
+    return m ? m[1] : null;
   }
 
   // ─── Private: PDF text extraction ──────────────────────────────────────────

apps/api/src/dkv/providers/exchange-inbox.provider.ts

@@ -24,14 +24,22 @@ function soapEnvelope(body: string): string {
 }
 
 function findItemSoap(folderId: string, maxResults: number, senderFilter?: string): string {
+  const isReadFilter = `<t:IsEqualTo>
+        <t:FieldURI FieldURI="message:IsRead"/>
+        <t:FieldURIOrConstant><t:Constant Value="false"/></t:FieldURIOrConstant>
+      </t:IsEqualTo>`;
+
   const restriction = senderFilter
     ? `<m:Restriction>
-        <t:Contains ContainmentMode="Substring" ContainmentComparison="IgnoreCase">
-          <t:FieldURI FieldURI="message:From"/>
-          <t:Constant Value="${escapeXml(senderFilter)}"/>
-        </t:Contains>
+        <t:And>
+          ${isReadFilter}
+          <t:Contains ContainmentMode="Substring" ContainmentComparison="IgnoreCase">
+            <t:FieldURI FieldURI="message:From"/>
+            <t:Constant Value="${escapeXml(senderFilter)}"/>
+          </t:Contains>
+        </t:And>
       </m:Restriction>`
-    : '';
+    : `<m:Restriction>${isReadFilter}</m:Restriction>`;
 
   return soapEnvelope(`
     <m:FindItem Traversal="Shallow">
@@ -71,6 +79,23 @@ function getItemSoap(itemIds: string[]): string {
     </m:GetItem>`);
 }
 
+function markReadSoap(itemId: string, changeKey: string): string {
+  return soapEnvelope(`
+    <m:UpdateItem MessageDisposition="SaveOnly" ConflictResolution="AlwaysOverwrite">
+      <m:ItemChanges>
+        <t:ItemChange>
+          <t:ItemId Id="${escapeXml(itemId)}" ChangeKey="${escapeXml(changeKey)}"/>
+          <t:Updates>
+            <t:SetItemField>
+              <t:FieldURI FieldURI="message:IsRead"/>
+              <t:Message><t:IsRead>true</t:IsRead></t:Message>
+            </t:SetItemField>
+          </t:Updates>
+        </t:ItemChange>
+      </m:ItemChanges>
+    </m:UpdateItem>`);
+}
+
 function getAttachmentSoap(attachmentId: string): string {
   return soapEnvelope(`
     <m:GetAttachment>
@@ -259,6 +284,7 @@ export class ExchangeInboxProvider implements InboxProvider {
 
       for (const block of messageBlocks) {
         const uid = extractAttr(block, 't:ItemId', 'Id');
+        const changeKey = extractAttr(block, 't:ItemId', 'ChangeKey');
         const subject = extractAll(block, 't:Subject')[0] ?? '';
         const messageId = extractAll(block, 't:InternetMessageId')[0] ?? '';
         const from = (extractAttr(block, 't:Mailbox', 'SmtpAddress') ||
@@ -317,6 +343,15 @@ export class ExchangeInboxProvider implements InboxProvider {
         if (attachments.length === 0) continue;
 
         results.push({ uid, messageId, subject, from, date, attachments });
+
+        // Mark as read so subsequent polls skip this message (mirrors IMAP \Seen flag).
+        if (uid && changeKey) {
+          try {
+            await this.ewsPost(config, markReadSoap(uid, changeKey), 'UpdateItem');
+          } catch {
+            // Non-fatal: message will reappear on next poll but IsRead filter will catch it
+          }
+        }
       }
     }