docs: aggiungi avatar del tema e referenzialo nel README

- preview/avatar.png: emblema 512x512 nello stile del tema (immagine
  generata con IA, non coperta dalle licenze di audio e codice)
- README: mostra l'avatar in testa e chiarisce la licenza dell'immagine
- dist/: tarball aggiornato

README.md

@@ -1,5 +1,7 @@
 # Interstellar — sound theme for KDE Plasma
 
+<img src="preview/avatar.png" alt="Interstellar" width="120" align="right">
+
 *A long look out of the window*
 
 A complete, [freedesktop Sound Theme
@@ -19,7 +21,9 @@ kde-sound-theme-interstellar/
 │   ├── verify_theme.py      # spec + audio + KDE coverage checks
 │   ├── make_preview.py      # rebuilds preview/index.html
 │   └── preview_template.html
-├── preview/index.html
+├── preview/
+│   ├── index.html           # player nel browser per ogni cue
+│   └── avatar.png           # icona del tema (512×512)
 ├── LICENSES/
 ├── Makefile
 └── install.sh
@@ -230,3 +234,8 @@ adapt it freely, subject to CC BY-SA 4.0's attribution and share-alike terms.
 ## Credits
 
 Created by **enne2** (2026). Designed for Plasma 6.3 on Debian 13.
+
+The avatar illustration in `preview/avatar.png` is an AI-generated image (Google
+Gemini via Antigravity). It is included only to identify the theme, and is **not**
+covered by either grant below: neither the CC BY-SA 4.0 that applies to the audio
+nor the BSD-2-Clause that applies to the code.