update slides styling and content refinements

- fix course number 223015c → 223015b in termin 1
- adjust language: "fuck" → "heck" in example
- add black backgrounds for image-only slides
- add bg fit to fullscreen images
- update digital-landscape.png
- add frontmatter to termin 2-4 slides

slides/2026-01-23-termin-3-speichermedien-schnittstellen.md

@@ -18,8 +18,20 @@ h2 {
 </style>
 
 <!-- _class: invert -->
+<!-- _header: '' -->
+<!-- _backgroundColor: #000 -->
 
-![bg fit](./assets/digital-landscape.png)
+![bg fit opacity:0.4](./assets/digital-landscape.png)
+
+# Dateiformate, Schnittstellen, Speichermedien & Distributionswege
+
+**223015b** · Modul "Technik 1" · 1. Semester
+Digital- und Medienwirtschaft
+Hochschule der Medien Stuttgart
+
+**Wintersemester 2025/26**
+
+[https://git.librete.ch/hdm/223015b](https://git.librete.ch/hdm/223015b)
 
 ---