refactor: share common files between images; trim fedora-remote for a VM

- Move Kanidm/flatpak/finalize.d/sshd files to images/shared/{files,repos}
  and have build.sh overlay them for every image.
- fedora-remote: aggressive hardware trim (no firmware, no kernel-modules-extra,
  no non-QEMU guest agents), keep + enable qemu-guest-agent (Proxmox).
- Fixes the missing package-list (release step) for fedora-remote.

build.sh

@@ -179,6 +179,16 @@ case "${BUILD_MODE}" in
     if [[ -d "${IMAGE_DIR}/files" ]]; then
       cp -a "${IMAGE_DIR}/files/." "${BUILD_DIR}/upstream/"
     fi
+    # Shared overlay (files/repos used by multiple images).
+    if [[ -d "${REPO_ROOT}/images/shared/files" ]]; then
+      cp -a "${REPO_ROOT}/images/shared/files/." "${BUILD_DIR}/upstream/"
+    fi
+    if compgen -G "${REPO_ROOT}/images/shared/repos/*.repo" >/dev/null; then
+      cp "${REPO_ROOT}"/images/shared/repos/*.repo "${BUILD_DIR}/upstream/"
+    fi
+    if compgen -G "${REPO_ROOT}/images/shared/repos/${DISTRO}/*.repo" >/dev/null; then
+      cp "${REPO_ROOT}"/images/shared/repos/"${DISTRO}"/*.repo "${BUILD_DIR}/upstream/"
+    fi
 
     if [[ "${TOKEN2}" == "1" ]]; then
       setup_token2_repo "${BUILD_DIR}/upstream"
@@ -209,6 +219,9 @@ case "${BUILD_MODE}" in
     if compgen -G "${local_dir}/repos/${DISTRO}/*.repo" >/dev/null; then
       cp "${local_dir}"/repos/"${DISTRO}"/*.repo "${local_dir}/"
     fi
+    if [[ -d "${REPO_ROOT}/images/shared/files" ]]; then
+      cp -a "${REPO_ROOT}/images/shared/files/." "${local_dir}/"
+    fi
 
     if [[ "${TOKEN2}" == "1" ]]; then
       setup_token2_repo "${local_dir}"