Add first-boot wizard for pre-built RPi images

- Create first-boot-wizard.sh with interactive step-by-step setup
  - Step 1: HTTPS configuration
  - Step 2: Port 443 configuration (if HTTPS enabled)
  - Step 3: Channel key generation
  - ASCII art banner and clear summaries
- Create stegasoo-wizard.sh profile.d hook to trigger wizard on SSH login
- Update sanitize-for-image.sh to:
  - Install wizard hook in /etc/profile.d/
  - Create first-boot flag file
  - Reset service to defaults for fresh config

Users who flash a pre-built image will see the wizard on first SSH login.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

rpi/stegasoo-wizard.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# Stegasoo First Boot Wizard Trigger
+# This file goes in /etc/profile.d/ and runs the wizard on first login
+
+if [ -f /etc/stegasoo-first-boot ] && [ -f /home/*/stegasoo/rpi/first-boot-wizard.sh ]; then
+    # Find the wizard script
+    WIZARD=$(ls /home/*/stegasoo/rpi/first-boot-wizard.sh 2>/dev/null | head -1)
+    if [ -n "$WIZARD" ]; then
+        bash "$WIZARD"
+    fi
+fi