Configure Gitea Workflows and Add Build Scripts

- Update build-linux.yaml to use standard Ubuntu runner.
- Update build-windows.yaml to use tobix/pywine container for cross-compilation on Linux.
- Add build_app.py and check_ttx6.py helper scripts.

check_ttx6.py

@@ -0,0 +1,28 @@
+
+import sys
+import os
+
+# Add src to path
+sys.path.append(os.path.join(os.getcwd(), 'src'))
+
+from teletext.io import load_t42
+
+def check_file(filename):
+    if not os.path.exists(filename):
+        print(f"File {filename} not found")
+        return
+
+    service = load_t42(filename)
+    print(f"Analysis of {filename}:")
+    print(f"Total packets: {len(service.all_packets)}")
+    print(f"Total pages: {len(service.pages)}")
+    
+    language_names = ["English", "German", "Swedish/Finnish", "Italian", "French", "Portuguese/Spanish", "Turkish", "Romania"]
+    
+    for i, page in enumerate(service.pages):
+        lang_idx = page.language
+        lang_name = language_names[lang_idx] if 0 <= lang_idx < len(language_names) else f"Unknown ({lang_idx})"
+        print(f"Page {i+1}: Mag {page.magazine} Num {page.page_number:02d}, Lang: {lang_idx} ({lang_name})")
+
+if __name__ == "__main__":
+    check_file("TTX-6_RAW.t42")