docs: flip lockscreen references to hyprlock

Replace all gtklock mentions in README, ARCHITECTURE, CLAUDE.md with
hyprlock, and drop the stale gtklock consumer note from theme/colors.css
header comment (hyprlock uses Hyprlang, not CSS imports).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ARCHITECTURE.md

@@ -123,7 +123,7 @@ This system is a **Wayland-first desktop environment** built around the **Niri c
 
 ### Lock Screen
 
-#### gtklock
+#### hyprlock
 
 * Simple Wayland-native lockscreen
 
@@ -190,7 +190,7 @@ System → Waybar module → Display
 ├── starship.toml
 ├── mako/
 ├── wofi/
-└── gtklock/
+└── hyprlock/
 ```
 
 All configs are sourced from the repo via: