Fix language detection bit swap in T42 header parsing

Correctly map C12 and C13 control bits to fix misidentification of Swedish/Finnish (010) and German (001).
Also ensures Page model, Renderer, and UI properly propagate and display the detected language.

src/teletext/models.py

@@ -76,6 +76,7 @@ class Page:
     magazine: int
     page_number: int  # 00-99
     sub_code: int = 0 # Subpage code (0000 to 3F7F hex usually, simplest is 0-99 equivalent)
+    language: int = 0 # National Option (0-7)
     packets: List[Packet] = field(default_factory=list)
     
     @property