Web UI v4.1.6: Admin settings, nav icons, air-gap ready

Admin System Settings page:
- New /admin/settings route with channel key config
- QR code export with tiled print sheet (4x5 on US Letter)
- Server config display (HTTPS, port, auth, DCT/QR status)
- Environment info (version, Python, platform, KDF)

Navigation improvements:
- Icon-only nav with floating labels on hover
- Gold labels slide down below icons
- Gradient pill background on hover

Air-gap ready:
- All vendor libs now local (Bootstrap CSS/JS, Icons, html5-qrcode)
- QRious library for QR generation
- No external CDN dependencies

Other changes:
- Moved About link from nav to footer
- Channel QR export moved from about.html to admin/settings.html
- Print sheet button for QR codes (tiled US Letter output)
- Dev runner script (dev_run.sh) with r/q hotkeys
- Fixed navbar dropdown z-index

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

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

tests/test_stegasoo.py

@@ -5,27 +5,24 @@ Tests core functionality: encode/decode, LSB/DCT modes, channel keys, validation
 """
 
 import io
-import pytest
 from pathlib import Path
+
+import pytest
 from PIL import Image
 
 import stegasoo
 from stegasoo import (
-    encode,
     decode,
     decode_text,
+    encode,
+    generate_channel_key,
     generate_passphrase,
     generate_pin,
-    generate_channel_key,
-    validate_passphrase,
-    validate_pin,
+    has_dct_support,
     validate_image,
     validate_message,
-    has_dct_support,
-    EncodeResult,
-    DecodeResult,
-    ValidationError,
-    CapacityError,
+    validate_passphrase,
+    validate_pin,
 )
 
 # Test data paths