fix(policy): keep internal allowed IP proposals pending

[alangou]

Summary

Keep draft policy proposals pending when allowed_ips targets private or internal ranges. Re-evaluate auto-approval against the rule currently stored after edits and mechanistic deduplication so stale proposal analysis cannot bypass human review.

Related Issue

closes OS-188

Changes

• Classify IPv4 and IPv6 CIDRs that intersect private, internal, or special-use ranges
• Add advisory security notes for internal allowed_ips and hostless allowlists
• Recompute security notes and the auto-approval prover verdict from the stored draft rule
• Preserve hard rejection for destinations that the runtime always blocks
• Add regression coverage and update user-facing and architecture documentation

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (not applicable: no sandbox infrastructure change)

Additional validation: mise run lint and mise run test pass.

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

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