Capitalize Persian and make sure language is lowercase when being used.

src/srtify/core/models.py

@@ -43,7 +43,7 @@ class DirectoryConfig:
 @dataclass
 class TranslationConfig:
     """Translation configuration settings."""
-    default_language: str = "persian"
+    default_language: str = "Persian"
     batch_size: int = 300
 
     def __post_init__(self):

src/srtify/core/translator.py

@@ -42,7 +42,7 @@ class TranslatorApp:
 
         # Configure gemini_srt_translator
         gst.gemini_api_key = api_key
-        gst.target_language = language
+        gst.target_language = language.lower()
         gst.input_file = str(input_file)
         gst.output_file = str(output_file)
         gst.batch_size = batch_size