Sakura Line: retheme the whole desktop from the wallpaper

Palette sampled from bspwm/wallpaper/wallpaper.jpg and applied per-role
(not per-hex, so terminal green stays green and nvim's LineNr/Comment
stay recessive) across st, kitty, polybar, rofi, dunst, nvim, qt5ct/qt6ct
and GTK 2/3/4.

Also:
- rofi drun centred, icons enabled
- polybar translucent (true ARGB) and rounded; picom corner-radius, with
  the desktop layer and fullscreen windows excluded
- fix qt5ct color_scheme_path pointing at a nonexistent /home/carrie
- export QT_QPA_PLATFORMTHEME so qt6ct is actually consulted
- point GTK at an icon theme that exists on this system
- add .config/rice: one-shot install.sh (--dry-run supported), package
  list, vendored st config.h (gitignored upstream) and the particles
  wallpaper-layer source, so a clone reproduces the rice

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cn3dHfbgNYdbZvzb1b3GQt

.config/dunst/dunstrc

@@ -12,7 +12,7 @@ origin = top-right
 
 frame_width = 2
 separator_height = 1
-frame_color = "#8b9151"
+frame_color = "#92b9ea"
 separator_color = frame
 
 sort = no
@@ -33,7 +33,7 @@ sticky_history = no
 history_length = 6
 title = Dunst
 class = Dunst
-corner_radius = 0
+corner_radius = 12
 
 mouse_left_click = close_current
 mouse_middle_click = do_action
@@ -44,20 +44,20 @@ body = "grim's screenshot component is implemented based on wlroots, it may not
 format = ""
 
 [urgency_low]
-background = "#141414"
-foreground = "#8b9151"
-frame_color = "#8b9151"
+background = "#0f0d17"
+foreground = "#7f7796"
+frame_color = "#3d3752"
 timeout = 5
 
 [urgency_normal]
 default_icon = dialog-information
-background = "#141414"
-foreground = "#feffd3"
-frame_color = "#8b9151"
+background = "#0f0d17"
+foreground = "#e9eefb"
+frame_color = "#92b9ea"
 timeout = 5
 
 [urgency_critical]
-background = "#141414"
-foreground = "#dd7c4c"
-frame_color = "#dd7c4c"
+background = "#0f0d17"
+foreground = "#e0798f"
+frame_color = "#cf6a80"
 timeout = 0