ci: add rsync + AppImage host tools (file, libfuse2, desktop-file-utils)

After the QML/C++ build started succeeding, `make appimage` failed at
the staging-symfony step ("rsync: No such file or directory") — slim
runner image again. Adding:

  - rsync                — used by examples/todo/Makefile to stage a
                           --no-dev composer copy of the Symfony tree
                           into build/staging-symfony/.
  - file                 — appimagetool/linuxdeploy invoke `file` to
                           detect ELF type (AppImage, AppDir contents).
  - libfuse2             — AppImage runtime mounts the squashfs via
                           libfuse2; without it appimagetool refuses
                           to assemble. (Alternative is
                           APPIMAGE_EXTRACT_AND_RUN=1 but installing
                           libfuse2 keeps the script unchanged.)
  - desktop-file-utils   — appimagetool validates the bundled
                           .desktop file via desktop-file-validate.

ci.yml only needs cmake + ninja + rsync (the symfony staging happens
in `make build` which it runs too, after the QML build) — no AppImage
assembly there.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -50,8 +50,8 @@ jobs:
         with:
           python-version: '3.12'
 
-      - name: Install build tools (cmake, ninja)
-        run: sudo apt-get install -y cmake ninja-build
+      - name: Install build tools
+        run: sudo apt-get install -y cmake ninja-build rsync
 
       - name: Setup Qt 6
         uses: jurplel/install-qt-action@v4

.gitea/workflows/release.yml

@@ -33,8 +33,8 @@ jobs:
         with:
           python-version: '3.12'
 
-      - name: Install build tools (cmake, ninja)
-        run: sudo apt-get install -y cmake ninja-build
+      - name: Install build + AppImage tools
+        run: sudo apt-get install -y cmake ninja-build rsync file libfuse2 desktop-file-utils
 
       - name: Setup Qt 6
         uses: jurplel/install-qt-action@v4