hypr: make the per-host config lookup case-insensitive

The hosts files were written capitalized (Rutherford.lua, Chester.lua)
but the require uses the hostname exactly as `hostname` prints it —
lowercase — so on a case-sensitive filesystem the lookup missed and
pcall silently swallowed it. The per-host monitor overrides therefore
never loaded on either machine. Normalize the hostname to lowercase
and name the files in lowercase so any casing matches.

hypr/hosts/rutherford.lua

@@ -0,0 +1,9 @@
+-- Host-specific overrides: Rutherford (desktop PC)
+-- Loaded automatically by hyprland.lua via hostname detection.
+
+hl.monitor({
+    output   = "DP-1",
+    mode     = "2560x1440@74.97",
+    position = "0x0",
+    scale    = 1,
+})