4.1.4: QR sharing, venv tarball, flash script improvements

QR Channel Key Sharing:
- Admin-only QR generator in about.html (was visible to all)
- QR button for saved keys on account page
- Fixed about() route missing channel status vars (bug)

Pi Build Optimization:
- Pre-built venv tarball support (39MB zstd, skips 20+ min compile)
- setup.sh auto-detects and extracts tarball if present
- Strip __pycache__/tests before tarball (295MB → 208MB)

Flash Script Improvements:
- flash-image.sh now uses config.json for headless WiFi setup
- Consistent wipe prompt on both flash scripts
- pull-image.sh re-enables auto-expand before shrinking

Build Docs:
- Added zstd and jq to pre-setup apt-get
- Documented fast build option with pre-built venv

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

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

frontends/web/app.py

@@ -1561,7 +1561,25 @@ def decode_download(file_id):
 
 @app.route("/about")
 def about():
-    return render_template("about.html", has_argon2=has_argon2(), has_qrcode_read=HAS_QRCODE_READ)
+    from stegasoo.channel import get_channel_status
+
+    channel_status = get_channel_status()
+
+    # Check if user is admin (for QR sharing)
+    current_user = get_current_user()
+    is_admin = current_user.is_admin if current_user else False
+
+    return render_template(
+        "about.html",
+        has_argon2=has_argon2(),
+        has_qrcode_read=HAS_QRCODE_READ,
+        # Channel info (bugfix - was not being passed)
+        channel_configured=channel_status["configured"],
+        channel_fingerprint=channel_status.get("fingerprint"),
+        channel_source=channel_status.get("source"),
+        # Admin check for QR sharing
+        is_admin=is_admin,
+    )
 
 
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