docs: improve README SEO for BGP RPKI ROA validation

[DeepZone]

Motivation

• Improve README discoverability for routing-security and validation search terms while keeping RouteForge present but not the primary keyword.
• Make the intro explicitly focus on BGP, RPKI and ROA preflight validation and related operational keywords without over-promising capabilities.
• Preserve product constraints: read-only positioning, stable release status, and version v1.0.0.

Description

• Replaced the top title with BGP, RPKI and ROA Preflight Validation Tool and updated the short description under the badges to: Self-hosted read-only preflight validation for BGP, RPKI, ROA, RIPEstat, Registry/IRR and routing visibility workflows.
• Replaced the previous intro sections with What this tool does, Why BGP and RPKI preflight validation matters, Key Features, Typical Use Cases, and Current Release, and integrated the requested keywords (e.g., BGP visibility, RPKI validation, ROA preflight, ROA planning, RIPEstat, Registry/IRR, ASN checks, prefix-origin validation, routing visibility, route leak, origin mismatch, invalid announcement, self-hosted, read-only) naturally in context.
• Removed Alpha/Beta/RC phrasing and the versioned v0.8.1-beta label from the BGP visibility subsection heading, and kept the status badge as stable and version as v1.0.0.
• No code, configuration, database migrations, or frontend source files were modified; README content only. Suggested GitHub repository description: Self-hosted read-only BGP, RPKI, ROA and RIPEstat preflight validation tool for routing changes, prefix-origin checks and routing visibility workflows.

Testing

• Ran grep -RInE "Alpha|Beta|RC|v0\.|deutsch|Prüfung|Fehler|Benutzer|Passwort|ä|ö|ü|ß" README.md and verified there are no matches in README.md after the edits.
• No frontend build was run because no frontend files were changed.
• No automated backend tests were required or run as part of this docs-only change.

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Codex Task