Prepare v0.1.0-alpha demo documentation, example reports and UI microcopy

[DeepZone]

Motivation

• Prepare RouteForge for a presentable v0.1.0-alpha demo with reproducible demo artifacts and clear operator-facing guidance.
• Provide demo-focused example reports and a screenshot plan so demos can be prepared without creating or shipping production data.
• Improve small UI microcopy items to make report and form texts clearer for network operators while preserving existing behavior and the read-only model.

Description

• Add RELEASE_NOTES.md for v0.1.0-alpha containing overview, included features, exclusions, read-only security model, demo-mode guidance, known limitations, an example flow, and next steps.
• Add demo example reports under examples/reports/ (prefix-valid-warning-example.md and asn-rpki-batch-demo-example.md) and add a screenshot plan at docs/screenshots/README.md listing the planned images.
• Extend README.md with an Alpha Demo Flow section and explicit known limitations to match the release notes.
• Update small UI microcopy in frontend/src/components/AsnCheckForm.tsx and frontend/src/components/ReportView.tsx to clarify ASN vs RPKI behavior, rename a few labels (e.g. Summary→Kurzfassung) and make the report copy button text clearer, without changing API or endpoint behavior.

Testing

• Ran backend tests with cd backend && pytest -q which completed successfully (35 passed, 20 warnings).
• Built the frontend with cd frontend && npm run build, and the production build completed successfully (Vite build finished).

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Codex Task