fix(deps): ignore undici in dependabot -- nested unreachable copy in npm's bundled tree

[asachs01]

Summary

Same root cause and fix as WYRE-AI/node-ninjaone#74: Dependabot's Security update job for undici fails silently (security_update_not_possible, no PR ever opens). The flagged copy is node_modules/npm/node_modules/undici@6.27.0, nested inside npm's own bundled dependency tree -- identical nested path and version to node-ninjaone's confirmed case, so relying on that repo's empirical override-pin verification rather than re-deriving.

Adds a dependabot ignore rule matching the existing ip-address entry's shape. The underlying GHSA alert stays visible on the Security tab regardless.

Test plan

• YAML validated
• Same nested path/version as the empirically-verified node-ninjaone case (fix(deps): ignore undici in dependabot -- nested unreachable copy in npm's bundled tree node-ninjaone#74)
• Config-only change, no source/dependency changes

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[asachs01]

Reviewed (maintainer). Verified against real artifacts, not just the description:

• Pulled this repo's own package-lock.json directly and confirmed node_modules/npm/node_modules/undici@6.27.0 — the exact nested npm-bundled copy claimed, at the exact version. Cross-checked this against all 6 sibling repos in the same batch: identical nested path AND version in every one, which independently corroborates the "same npm toolchain, same bundled tree" reasoning behind reusing the override-pin mechanism test rather than re-running it per repo.
• The override-pin mechanism itself (an overrides pin in a consumer's package.json cannot reach a dependency bundled inside the npm CLI package's own bundleDependencies) is a structural npm behavior, not repo-specific — it depends on which npm binary resolved the tree, not on anything in this repo's own manifest. Reusing a single empirical confirmation of that mechanism across repos sharing the identical nested version is sound, not a shortcut.
• No source changes, dependabot.yml-only diff, CI green, no branch protection on this repo (direct merge, no gate).

Verdict: approve