Fix Fedora DNF5 compatibility and distro-specific packages

Key changes:
- lib/distro.sh: replace REPO_ADD_RPM variable with repo_add_rpm()
  function (DNF5 changed 'config-manager --add-repo' to
  'config-manager addrepo --from-repofile=')
- 01-repos.sh: use repo_add_rpm function; add Ghostty COPR for
  Fedora; remove Signal RPM repo (no official one — use Flatpak)
- 02-packages.sh: lowercase 'development-tools' group for DNF5;
  add python3-devel (needed for native extensions like evdev);
  swap ffmpeg-free → ffmpeg via RPM Fusion for full codec support;
  use tuned (preinstalled on Fedora) instead of TLP
- 11-tweaks.sh: conditional power management — TLP on Debian,
  tuned on Fedora

stages/01-repos.sh

@@ -171,31 +171,25 @@ EOF
 
   # ---- Docker CE ----
   info "  Adding Docker CE repo..."
-  $REPO_ADD_RPM https://download.docker.com/linux/fedora/docker-ce.repo 2>/dev/null && \
+  repo_add_rpm https://download.docker.com/linux/fedora/docker-ce.repo && \
     ok "  Docker repo added." || warn "  Docker repo add failed."
 
   # ---- Tailscale ----
   info "  Adding Tailscale repo..."
-  $REPO_ADD_RPM https://pkgs.tailscale.com/stable/fedora/tailscale.repo 2>/dev/null && \
+  repo_add_rpm https://pkgs.tailscale.com/stable/fedora/tailscale.repo && \
     ok "  Tailscale repo added." || warn "  Tailscale repo add failed."
 
   # ---- Signal Desktop ----
-  info "  Adding Signal repo..."
-  cat << 'EOF' | sudo tee /etc/yum.repos.d/signal-desktop.repo > /dev/null
-[signal-desktop]
-name=Signal Desktop
-baseurl=https://updates.signal.org/desktop/yum
-enabled=1
-gpgcheck=1
-gpgkey=https://updates.signal.org/desktop/signal_pubkey.gpg
-EOF
-  ok "  Signal repo added."
+  # Signal does not provide an official RPM repo. Install via Flatpak (handled in stage 12).
+  info "  Note: Signal will be installed via Flatpak in stage 12."
 
   # ---- COPRs for extra packages ----
   # Papirus icon theme is in RPM Fusion nonfree.
   # Solaar is in RPM Fusion.
   # Yubico tools: use COPR
   info "  Adding COPR repos..."
+  # Ghostty terminal emulator
+  $REPO_ADD_COPR scottames/ghostty 2>/dev/null && ok "  Ghostty COPR added." || warn "  Ghostty COPR failed."
   # $REPO_ADD_COPR atim/papirus-icon-theme 2>/dev/null || true
   # $REPO_ADD_COPR sergiomb/Solaar 2>/dev/null || true