Replace swaylock with gtklock; centralise theme palette

- Replace swaylock with gtklock (username + password form lockscreen)
- Add gtklock/config.ini and gtklock/style.css (Tomorrow Night theme)
- Update niri keybindings and swayidle to invoke gtklock -d
- Update packages.txt: swaylock -> gtklock
- Update install.sh: add AUR helper detection (yay/paru), symlink gtklock configs
- Add theme/colors.css (CSS custom properties) and theme/colors.json
- Update waybar/style.css, wofi/style.css, gtklock/style.css to import shared palette
- Update README.md with project summary and component table
- Add ARCHITECTURE.md and CLAUDE.md

waybar/style.css

@@ -1,20 +1,22 @@
+@import url("../theme/colors.css");
+
 * {
   font-family: JetBrainsMono Nerd Font;
   font-size: 13px;
 }
 
 window#waybar {
-  background: rgba(29,31,33,0.9);
-  color: #c5c8c6;
+  background: var(--tn-bg-a90);
+  color: var(--tn-fg);
 }
 
 #workspaces button {
   padding: 0 8px;
-  color: #707880;
+  color: var(--tn-fg-muted);
 }
 
 #workspaces button.focused {
-  color: #81a2be;
+  color: var(--tn-blue);
 }
 
 #clock, #battery, #network, #pulseaudio,
@@ -24,33 +26,33 @@ window#waybar {
 }
 
 #custom-power-profile.performance {
-  color: #f0c674;
+  color: var(--tn-yellow);
 }
 
 #custom-power-profile.power-saver {
-  color: #b5bd68;
+  color: var(--tn-green);
 }
 
 #battery.warning {
-  color: #f0c674;
+  color: var(--tn-yellow);
 }
 
 #battery.critical {
-  color: #cc6666;
+  color: var(--tn-red);
 }
 
 #cpu.warning {
-  color: #f0c674;
+  color: var(--tn-yellow);
 }
 
 #cpu.critical {
-  color: #cc6666;
+  color: var(--tn-red);
 }
 
 #temperature.warm {
-  color: #f0c674;
+  color: var(--tn-yellow);
 }
 
 #temperature.critical {
-  color: #cc6666;
+  color: var(--tn-red);
 }