Draft: Convert SPA router roots via the SpaRouterView helper

What does this MR do and why?

Stacked on !247299 (merged) (the boring initVueApp wave) — retarget to master when it merges. Six bootstraps mount single-page apps whose root render is just a router-view; the SpaRouterView helper in vue_shared/spa expresses that root once in a dual-runtime shape instead of each bootstrap hand-writing a render function. The helper and its spec convert alongside the six usages so the whole pattern reviews in one place.

Converted bootstraps: environments (folder + show), dependency proxy, EE instance model selection, EE compliance dashboard, EE security configuration.

Content is the exact CI-proven state from the pre-split !247299 (merged).

MR acceptance checklist

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