ci: build AppImage and deb in CI; flatpak stays local

flatpak-builder cannot run inside the job container.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -14,20 +14,17 @@ jobs:
       - name: Tools
         run: |
           apt-get update
-          apt-get install -y flatpak flatpak-builder fakeroot dpkg rpm libarchive-tools
-          flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
-          flatpak install -y flathub org.freedesktop.Platform//25.08 org.freedesktop.Sdk//25.08 org.electronjs.Electron2.BaseApp//25.08
+          apt-get install -y fakeroot dpkg rpm libarchive-tools
           npm i -g bun
       - run: bun install --frozen-lockfile --ignore-scripts
       - run: bun run build
-      - run: bunx electron-builder --linux AppImage deb flatpak
+      - run: bunx electron-builder --linux AppImage deb
       - uses: actions/upload-artifact@v3
         with:
           name: linux
           path: |
             dist/*.AppImage
             dist/*.deb
-            dist/*.flatpak
 
   windows:
     runs-on: ubuntu-latest