Add text ellipsization and monospace font to GTK GUI

[TheZupZup]

Overview

Two specific readability gaps exist in the GTK GUI (main.py):

1. Long process names (e.g. firefox-esr, /usr/lib/chromium/chromium) overflow their column or get cut off abruptly with no visual indicator that text is truncated.
2. The activity log text view uses the default GTK font, which is a proportional font. Log output (timestamps, IPs, process names) reads much better in monospace.

What needs to be done

• For the Process column's CellRendererText, set ellipsization: renderer.set_property("ellipsize", Pango.EllipsizeMode.END) — this shows "firefox-e…" instead of a hard cut
• Import Pango at the top of main.py (via from gi.repository import Pango)
• For the activity log Gtk.TextView, set a monospace font: log_view.modify_font(Pango.FontDescription("Monospace 10"))

Goal

Long process names are ellipsized cleanly, and the activity log uses a monospace font for readable alignment.

Notes

Both changes are purely visual — no logic changes needed. This is a good first issue for anyone learning PyGObject.