chore: remove stale removeViewBox override from svgo preset-default config

[ericfitz]

Summary

src/app/pages/dfd/application/services/app-svg-optimization.service.ts:28-32 passes removeViewBox: false as a preset-default override. svgo v4 removed removeViewBox from the default preset, so the override is a no-op that fires a console warning on every SVG export:

You are trying to configure removeViewBox which is not part of preset-default.

Intent (preserve viewBox) is already satisfied by svgo 4's defaults; the stale override just adds noise.

Acceptance Criteria

• Remove the stale override (both config sites — line ~28 object form and line ~86 string-list form if applicable).
• SVG export produces no svgo warnings; exported SVG retains its viewBox.

Notes

Surfaced during #446 smoke testing (2026-08-03); confirmed pre-existing — the x6 branch never touched this file.