Refactor first-boot process to introduce ordered execution and new one-shot scripts

Revise the first-boot script to implement a structured approach with 13 numbered steps, allowing for better control over the execution order. Introduce two new one-shot scripts: `01-set-rotation-once.sh` and `02-set-wallpaper-once.sh`, replacing the previous single script approach. Update documentation to reflect these changes, including the new configuration options for enabling/disabling steps and the revised file structure for one-shot scripts. Enhance the dashboard to display first-boot progress, improving user feedback during the initial setup.

emmc-provisioning/cloud-init/02-set-wallpaper-once.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+# One-shot: set desktop wallpaper for labwc (swaybg) and persist via labwc autostart, then remove self.
+# Runs as user pi at first login. Logs to /var/log/first-boot.log.
+FIRST_BOOT_LOG="/var/log/first-boot.log"
+BASE="$(basename "$0" .sh)"
+log() { echo "[$(date -Iseconds)] [$BASE] $*" >> "$FIRST_BOOT_LOG" 2>/dev/null || true; }
+
+WALLPAPER="/usr/share/rpd-wallpaper/splash.png"
+LABWC_AUTOSTART="$HOME/.config/labwc/autostart"
+
+log "started (labwc/swaybg)"
+log "waiting 8s for compositor ..."
+sleep 8
+
+if [[ ! -f "$WALLPAPER" ]]; then
+  log "WARNING: wallpaper not found $WALLPAPER"
+else
+  mkdir -p "$(dirname "$LABWC_AUTOSTART")"
+  if [[ ! -f "$LABWC_AUTOSTART" ]]; then
+    echo '#!/bin/sh' > "$LABWC_AUTOSTART"
+    chmod +x "$LABWC_AUTOSTART"
+  fi
+  if ! grep -q 'swaybg.*splash.png' "$LABWC_AUTOSTART" 2>/dev/null; then
+    echo "swaybg -i $WALLPAPER -m fill &" >> "$LABWC_AUTOSTART"
+    log "added swaybg to labwc autostart"
+  fi
+  if command -v swaybg &>/dev/null; then
+    log "applying wallpaper now: $WALLPAPER"
+    swaybg -i "$WALLPAPER" -m fill &
+  else
+    log "WARNING: swaybg not installed"
+  fi
+fi
+
+log "removing one-shot desktop and script"
+rm -f "$HOME/.config/autostart/${BASE}.desktop" "$HOME/${BASE}.sh"
+log "finished"