ci: add dnf cache

containers/fedora/Containerfile

@@ -1,12 +1,12 @@
 FROM quay.io/fedora/fedora:43
 
 # === install system packages ===
-RUN dnf update -y && \
+RUN --mount=type=cache,id=dnf,target=/var/cache/libdnf5 \
+  dnf update -y && \
   dnf copr enable -y atim/lazygit && \
-  dnf -y install procps ping bash-completion glibc-langpack-en \
+  dnf -y --setopt=keepcache=1 install procps ping bash-completion glibc-langpack-en \
     host-spawn dbus-launch \
-    zoxide git npm neovim awk jq unzip fd-find lazygit && \
-  dnf clean all
+    zoxide git npm neovim awk jq unzip fd-find lazygit
 
 # === setup user ===
 RUN useradd -ms /bin/bash user && \