Replace xautolock with xss-lock, xidle-dim and xidle-inhibit

The screen dims after 590s and locks 10s later with i3lock-color through the new
screen-lock script; DPMS turns it off after 15 minutes.

.local/bin/screen-lock

@@ -0,0 +1,14 @@
+#!/bin/sh
+# i3lock-color with a background image and the keyboard layout shown.
+
+image=/usr/share/backgrounds/arch_1920x1080.png
+
+# -n: stay in the foreground, as xss-lock needs to see when the screen is unlocked.
+# --indicator keeps the ring (and the layout text) visible before typing.
+# The layout's default spot (dx:dy+30) falls inside the ring: put it below.
+exec i3lock -n -i "$image" -F -c 000000ff \
+    -e -f --indicator --keylayout 0 \
+    --layout-pos='ix:iy+r+40' --layout-color=ffffffff \
+    --layout-size=24 \
+    --time-color=ffffffff --date-color=ffffffff --date-str='%A, %d %B' \
+    --ring-color=1793d1ff --line-uses-ring "$@"