v4.1.5: Accordion UI, webcam QR scanning, Pi image fix

Encode/Decode UI:
- New accordion layout with 3 steps (encode) / 2 steps (decode)
- Gold step numbers with checkmarks on completion
- Dynamic right-aligned summaries as fields are filled
- Subtle gradient highlight on active accordion step

Webcam QR Scanning:
- Camera button for RSA key QR codes on encode/decode pages
- Camera button for channel key scanning
- 3-2-1 countdown capture for dense QR codes
- Proper scanner stop/restart on retry
- Backend decompression for STEGASOO-Z: compressed keys

RSA Key Print:
- Removed identifying text from QR print output
- Now prints plain QR code for discretion

Pi Image Script:
- Fixed 16GB resize to detect expand vs shrink
- Fresh images now properly EXPAND to 16GB
- Already-expanded images properly SHRINK to 16GB

UI Polish:
- Removed PIN helper text for compactness
- Fixed QR drop zone centering
- Fixed decode page element IDs for JS

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

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

frontends/web/templates/base.html

@@ -101,6 +101,8 @@
     </footer>
 
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
+    <!-- QR Code scanning library (v4.1.5) -->
+    <script src="https://unpkg.com/html5-qrcode@2.3.8/html5-qrcode.min.js"></script>
     <script>
     // Initialize toasts (auto-hide after delay)
     document.querySelectorAll('.toast').forEach(el => new bootstrap.Toast(el));