ci: GTK4/libadwaita/SDL3 dev packages for punktfunk-client-linux

Baked into the rust-ci image, plus an idempotent apt step in the rust
job itself — ci.yml runs against the previous push's image (docker.yml
bootstrap note), so the image change alone would leave this push and
the next one red.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ci/rust-ci.Dockerfile

@@ -20,6 +20,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libpipewire-0.3-dev libopus-dev libwayland-dev libxkbcommon-dev \
     # zerocopy link deps (GL via libglvnd, EGL, GBM)
     libgl-dev libegl-dev libgbm-dev \
+    # punktfunk-client-linux (GTK4/libadwaita shell, SDL3 gamepads)
+    libgtk-4-dev libadwaita-1-dev libsdl3-dev \
     && rm -rf /var/lib/apt/lists/*
 
 # libcuda link stub: the NVIDIA userspace library (no kernel module needed) provides