test: umfangreiche Testdaten (alle Dateitypen + Mail-Anhaenge)

- oCIS /testdata/: Bilder (jpg/png/webp/bmp/gif/tiff/svg), Audio (mp3/ogg/m4a/
  flac/wav), Video (mp4), PDFs (Text + Scan), Office (docx/xlsx/pptx), Text/Daten
  (md/txt/csv/json/xml/yaml/html/py/vcf/ics), Archive (zip/tar.gz).
- Maildir: Mails mit diversen Anhaengen (PDF/Bild/Word/Excel/MP3/MP4/PPTX/ZIP).
- TestFileTypes: read_file je Typ -> Content-Typ pruefen (image/text/resource).
- Generatoren tests/testdata/gen_testfiles.py + gen_maildir.py + upload_ocis.sh.
68 Tests gruen (vorher 54). Doku in MCPTEST.md.

tests/testdata/maildir/mcp-test-mail/INBOX/cur/1781848411.M897192P2002983Q8.polo:2,S

@@ -0,0 +1,43 @@
+Content-Type: multipart/mixed; boundary="===============1387712317359960679=="
+MIME-Version: 1.0
+From: projekt@example.com
+To: mcptest@local
+Subject: Projektdateien
+Date: Tue, 17 Jun 2026 10:00:00 +0200
+
+--===============1387712317359960679==
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: base64
+
+QXJjaGl2IHVuZCBOb3RpemVuLg==
+
+--===============1387712317359960679==
+Content-Type: application/octet-stream
+MIME-Version: 1.0
+Content-Transfer-Encoding: base64
+Content-Disposition: attachment; filename="archive.zip"
+
+UEsDBBQAAAAAAG8+01xNvKCxLQAAAC0AAAAJAAAAbm90ZXMudHh0RWluZmFjaGUgVGV4dGRhdGVp
+LgpaZWlsZSAyLgpVbWxhdXRlOiBhZW9ldWUKUEsDBBQAAAAAAG8+01wa5IaIGQAAABkAAAAIAAAA
+ZGF0YS5jc3ZuYW1lLHdlcnQKQWxwaGEsMQpCZXRhLDIKUEsBAhQDFAAAAAAAbz7TXE28oLEtAAAA
+LQAAAAkAAAAAAAAAAAAAALCBAAAAAG5vdGVzLnR4dFBLAQIUAxQAAAAAAG8+01wa5IaIGQAAABkA
+AAAIAAAAAAAAAAAAAACwgVQAAABkYXRhLmNzdlBLBQYAAAAAAgACAG0AAACTAAAAAAA=
+
+--===============1387712317359960679==
+Content-Type: application/octet-stream
+MIME-Version: 1.0
+Content-Transfer-Encoding: base64
+Content-Disposition: attachment; filename="notes.txt"
+
+RWluZmFjaGUgVGV4dGRhdGVpLgpaZWlsZSAyLgpVbWxhdXRlOiBhZW9ldWUK
+
+--===============1387712317359960679==
+Content-Type: application/octet-stream
+MIME-Version: 1.0
+Content-Transfer-Encoding: base64
+Content-Disposition: attachment; filename="data.csv"
+
+bmFtZSx3ZXJ0CkFscGhhLDEKQmV0YSwyCg==
+
+--===============1387712317359960679==--