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/11-tweaks.sh

@@ -15,7 +15,15 @@ CONFIG_DIR="${SCRIPT_DIR:-$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)}/conf
 # ===========================================================================
 info "Configuring power management..."
 
-$SERVICE_ENABLE tlp 2>/dev/null && ok "TLP enabled." || warn "TLP not available."
+# Enable TLP on Debian, tuned (already enabled) on Fedora
+if [ "$DISTRO_FAMILY" = "debian" ]; then
+  $SERVICE_ENABLE tlp 2>/dev/null && ok "TLP enabled." || warn "TLP not available."
+else
+  # tuned is already enabled from stage 02
+  if systemctl is-active tuned &>/dev/null; then
+    ok "tuned is running (enabled in stage 02)"
+  fi
+fi
 
 if command -v powertop &>/dev/null; then
   # Enable powertop auto-tune via systemd service