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/rice/particles/Makefile

@@ -0,0 +1,23 @@
+PREFIX ?= /usr/local
+BINDIR ?= $(PREFIX)/bin
+
+PKGS   := cairo x11 xext xfixes xrender xrandr
+CFLAGS ?= -O2 -Wall -Wextra
+CFLAGS += $(shell pkg-config --cflags $(PKGS))
+LDLIBS := $(shell pkg-config --libs $(PKGS)) -lm
+
+all: particles
+
+particles: particles_wall.c
+	$(CC) $(CFLAGS) -o $@ $< $(LDLIBS)
+
+install: particles
+	install -Dm755 particles $(DESTDIR)$(BINDIR)/particles
+
+uninstall:
+	rm -f $(DESTDIR)$(BINDIR)/particles
+
+clean:
+	rm -f particles
+
+.PHONY: all install uninstall clean