fix: mount pseudo-fs during install, simplify partitioning, and add mount point config

iridium_installer/ui/pages/welcome.py

@@ -50,6 +50,19 @@ class WelcomePage(Adw.Bin):
         dropdown = Gtk.DropDown.new_from_strings(languages)
         box.append(dropdown)
 
+        # Mount Point Entry
+        mount_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=6)
+        mount_box.set_margin_top(24)
+        mount_label = Gtk.Label(label="Installation Root (Mount Point):")
+        mount_label.set_halign(Gtk.Align.START)
+        self.mount_entry = Gtk.Entry(text="/mnt")
+        mount_box.append(mount_label)
+        mount_box.append(self.mount_entry)
+        box.append(mount_box)
+
         page.set_child(box)
 
         self.set_child(page)
+
+    def get_mount_root(self):
+        return self.mount_entry.get_text()