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.

.gitea/workflows/build-linux.yaml

@@ -5,12 +5,7 @@ jobs:
   build:
     name: Build Linux
     runs-on: ubuntu-latest
-    container:
-        image: catthehacker/ubuntu:act-latest
     steps:
-      - name: Configure Git Redirect
-        run: git config --global url."http://192.168.50.24:3333/".insteadOf "http://server:3000/"
-
       - name: Checkout
         uses: actions/checkout@v3
 
@@ -21,7 +16,7 @@ jobs:
 
       - name: Install Dependencies
         run: |
-          python --version
+          python -m pip install --upgrade pip
           pip install -r requirements.txt
 
       - name: Build Executable
@@ -32,4 +27,4 @@ jobs:
         uses: actions/upload-artifact@v3
         with:
           name: TeletextEditor-Linux
-          path: dist/TeletextEditor_Linux
+          path: dist/TeletextEditor_Linux