fix: add GitHub server check to workflows and streamline CMake installation

.github/workflows/appimage.yml

@@ -14,6 +14,8 @@ on:
 
 jobs:
   build-appimage:
+    # Only run on GitHub, skip on Gitea
+    if: github.server_url == 'https://github.com'
 
     strategy:
       matrix:
@@ -31,12 +33,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y build-essential libglfw3-dev libglfw3 libglew-dev libglew2.2 \
             libglm-dev libpng-dev libopenal-dev libluajit-5.1-dev libvorbis-dev \
-            libcurl4-openssl-dev libgtest-dev squashfs-tools valgrind wget
-          # Install CMake >= 3.26
-          wget https://github.com/Kitware/CMake/releases/download/v3.27.9/cmake-3.27.9-linux-x86_64.sh
-          chmod +x cmake-3.27.9-linux-x86_64.sh
-          sudo ./cmake-3.27.9-linux-x86_64.sh --skip-license --prefix=/usr/local
-          rm cmake-3.27.9-linux-x86_64.sh
+            libcurl4-openssl-dev libgtest-dev cmake squashfs-tools valgrind
           # fix luajit paths
           sudo ln -s /usr/lib/x86_64-linux-gnu/libluajit-5.1.a /usr/lib/x86_64-linux-gnu/liblua5.1.a
           sudo ln -s /usr/include/luajit-2.1 /usr/include/lua
@@ -67,4 +64,4 @@ jobs:
       - uses: actions/upload-artifact@v4
         with:
           name: AppImage
-          path: './*.AppImage*'
+          path: './*.AppImage*'