[codex] integrate Thumbmark identity graph and advanced QR editor

[MN-company]

What changed

• Add ThumbmarkJS collection on the redirect bounce page and persist /fp beacon data.
• Add Visitor / VisitorSignal schema, weighted signal matching, and selective Thumbmark API enrichment.
• Update the identity graph to render Thumbmark, canvas, audio, WebGL, device, timezone, IP, visit, and probable-match nodes.
• Add advanced QR customization with persisted Link.qr_config, PNG/SVG exports, colors, gradients, transparent background, dot styles, and centered logo upload.
• Add tests for /fp, Thumbmark signal matching, graph rendering, QR PNG/SVG generation, and QR config persistence.

Impact

This preserves legacy beacon/scoring behavior while adding a persistent identity graph backed by weighted Thumbmark signals, plus a richer QR editor for existing tracked links.

Validation

• python3 -m pytest -q -> 40 passed
• Alembic upgrade on temporary SQLite DB completed successfully through b79f4d9a66c1
• Pillow import verified (10.4.0 already present in requirements)
• Local QR server check: /dashboard/qr_view/qr-demo rendered editor controls; /dashboard/qr/qr-demo?format=png returned image/png; /dashboard/qr/qr-demo?format=svg returned valid SVG
• Earlier local browser check: tracking link redirected and POST /fp returned 204; DB populated thumbmark_hash, fp_canvas_hash, fp_audio_hash, and fp_webgl_hash