Validate network topology telemetry

[vikranthreddimasu]

• Summary: strictly validate peer bandwidth, latency, packet-loss, and MTU telemetry before route scoring.
• Summary: omit invalid local telemetry from advertisements, emit standards-compliant JSON, and reject link lists above the eight-link protocol limit.
• Security changes: malformed or oversized unauthenticated open-fleet topology data now fails closed; authentication and credential handling are unchanged.
• Usability changes: bad sensor or peer data can no longer create misleading route scores or invalid discovery payloads.
• Tests/checks run: focused topology and discovery tests passed (47 passed).
• Tests/checks run: make lint passed (Ruff plus mypy).
• Tests/checks run: full suite passed (1069 passed, 3 skipped, 2 warnings).
• Tests/checks run: wheel build, git diff --check, and diff-only secret scan passed.
• Tests/checks run: all 11 GitHub Actions checks passed.
• Commit: 4cc7c3a Validate peer network telemetry.
• Commit: 9a3ef5a Harden topology advertisements.
• Risks / manual review notes: low-risk parsing and serialization boundary change; older valid numeric JSON remains accepted; no auth, authorization, credential, destructive-action, or deployment-secret code changed.
• Merge status: merged into master after local and GitHub checks passed.