feat(languages): add Slovenian (sl) to the supported languages (#995)

Slovenian was missing from SUPPORTED_LANGUAGES, so the Settings picker did not offer it and normalize_language_shortcuts dropped any shortcut bound to it. Add it as a Whisper-only entry (whisper code sl; alphacephei publishes no Slovenian VOSK model), map the Slovenian XKB layout si to it for follow-keyboard-layout, and list it on the website languages page.

Fixes #970

src/vocalinux/utils/system_language.py

@@ -29,6 +29,7 @@ _LAYOUT_TO_LANGUAGE = {
     "gb": "en-us",
     "cz": "cs",
     "se": "sv",
+    "si": "sl",
     "dk": "da",
     "gr": "el",
     "ua": "uk",

src/vocalinux/utils/vosk_model_info.py

@@ -153,6 +153,11 @@ SUPPORTED_LANGUAGES = {
         "whisper": "ru",
         "vosk": "vosk-model-small-ru-0.22",
     },
+    "sl": {
+        "name": "Slovenian",
+        "whisper": "sl",
+        "vosk": None,
+    },
     "es": {
         "name": "Spanish",
         "whisper": "es",