Prepare the capstone release

[comwanga]

What changed

• Reframes BitScope around a learner-first home page, guided first-transaction journey, node readiness view, and clearer progressive navigation.
• Adds the release documentation set: architecture, curriculum map, threat model, scenario authoring, proof bundles, migration notes, release notes, limitations, supported Core versions, and release-readiness checklist.
• Replaces stale product captures with the six current learner/reviewer screenshots in both documentation trees.
• Adds a deterministic Chrome capture-and-verification script and CI screenshot inventory/mirror verification.
• Aligns the roadmap with the implemented Phases 0–11 and records CPFP/OP_RETURN as intentionally deferred follow-on work.

Why

This consolidates the completed capstone roadmap into a coherent first-run educational experience and makes the release artifacts reproducible. Documentation and screenshots now describe the current UI and the validated Bitcoin Core 28.1 workflow instead of older technical-console views.

Validation

• Backend: 319 passed using an isolated pytest temp/cache directory.
• Frontend: typecheck passed.
• Frontend: lint passed with three existing non-blocking warnings.
• Frontend: production build passed, including the new learner and node routes.
• docker compose config --quiet passed.
• scripts/capture-screenshots.ps1 -VerifyExisting passed.
• All six screenshots are 1440×1000 and byte-identical between docs/screenshots and docs-site/screenshots.
• No stale screenshot filenames or unresolved local documentation image references remain.
• git diff --check passed.