midscroll v1.11

Feature release adding a settings GUI and a click-to-toggle scroll mode, plus
security hardening across the daemon and session helper. Toggle mode was
requested in #1 by @ionburger.

Added

• Settings GUI (midscroll-settings). A GTK4 window to change every
  tunable - speed, dead zone, event rate, natural scrolling, the app blacklist
  and the new toggle mode - with no terminal or config editing. Changes are
  written by a small privileged helper (midscroll-apply) through pkexec,
  which restarts the daemon so they take effect immediately.
• Toggle mode (TOGGLE_MODE). Click the middle button once to start
  autoscroll and again - or any click - to stop it (Windows-Explorer / Firefox
  style) instead of holding and dragging. Off by default; enable it in the GUI
  or the config. Requested in #1 by @ionburger.
• Themed app icon. The scroll-arrows badge artwork now doubles as the
  settings app icon, so the launcher and Wayland window icon match the badge.

Security

• Sandboxed the daemon and the session helper. The overlay now runs with
  NoNewPrivileges, ProtectSystem, and kernel/clock/namespace
  with a restricted address-family set; the daemon gained a syscall filter
  (@system-service, EPERM) and MemoryDenyWriteExecute.
• Bounded the one input crossing the pkexec boundary. The blacklist value
  passed to midscroll-apply is now stripped of anything that is
  plausible window-class character and length-capped, so it can't mangle the
  config or carry a malformed payload.
• Shipped a polkit policy for midscroll-apply (auth_admin_keep), so
  applying settings uses a scoped, briefly-cached authorization i
  generic full-admin auth.
• Hardened self-recognition. The daemon refuses to grab its o
  mirrors even if the phys marker fails, and warns at startup if the marker
  doesn't round-trip - closing a hotplug window that could feed r
  back on itself.

Fixed

• Scroll badge and app blacklist under the new sandbox. kdoto
  real, shared, writable /tmp to hand KWin its script; the overlay now uses
  ProtectSystem=full (not strict) and no PrivateTmp, which
  broken the badge and focus reporting.
• Settings window height. The window now opens tall enough to
  control, capped to the monitor height so it never runs off a small screen.

Notes

• Middle-drag remains hold-and-drag by default; toggle mode is op
• You are encouraged to review the source yourself - it runs as root at the
  input layer. See the Security section of the README.
• Packaging bumped for Fedora (RPM), Debian (deb), and Arch (PKGBUILD).

Full changelog: v1.6...v1.11