fix(#474): style the scrollbar for Firefox too

[jarik2014]

Closes #474

What changes

src/app/globals.css styles the scrollbar with ::-webkit-scrollbar and friends. Chromium honours those; Firefox ignores them entirely, so the app has a themed scrollbar in Chrome and the platform default in Firefox. The issue points at the right block.

Firefox needs the standard properties, and they are inherited, so one declaration on the root covers the document:

html {
  scrollbar-width: thin;
  scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
}

thin is the closest match to the 10px the webkit block sets. Firefox has no hover state for the thumb, so --scrollbar-thumb-hover stays a Chromium-only refinement rather than something the two engines can share — worth knowing before someone reports the hover effect as missing on Firefox.

The four values moved into custom properties, because both syntaxes need the same colours and hard-coding #2a2f2d twice is exactly how they drift apart. That is this issue's failure mode — one engine styled, the other forgotten — so removing the duplication seemed worth the three extra lines. --scrollbar-thumb matches app.border's dark value in src/lib/theme.ts; if you would rather have one source of truth, the CSS variable could read from the theme instead of restating the hex, but I did not want to restructure the theme in a scrollbar fix.

Verification

Compiled the stylesheet with the project's own postcss pipeline (@tailwindcss/postcss, the plugin the build uses) and read the output rather than the source:

scrollbar-width: thin
scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track)
--scrollbar-thumb: #2a2f2d
--scrollbar-thumb-hover: #3a413e
--scrollbar-track: transparent
--scrollbar-size: 10px
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 999px }
::-webkit-scrollbar-thumb:hover { background: var(--scrollbar-thumb-hover) }

All four webkit rules survive the move to variables, so the change is purely additive: nothing about the Chromium rendering changes, and the Firefox path now exists.

next build could not be used as the check — it fails on a webpack error that originates in src/hooks/useLockFlow.ts, a file this PR does not touch (git diff origin/main -- src/hooks/useLockFlow.ts is empty). Worth its own issue, since it means the app cannot be built from a clean checkout of main; happy to dig in if you want, but I did not want to bundle it here.

One thing I did not do: there is no automated check that Firefox picks these up, because there is no Firefox in this repo's test setup. If the visual-regression suite ever runs a second project, scrollbar-width/scrollbar-color could be asserted there; a unit test would only be asserting my own string.

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[jarik2014]

Added one more commit: a lockfile sync that is not about this PR's own subject, but is the reason every Netlify check on this PR was red.

package.json has carried next-intl: ^4.14.6 while pnpm-lock.yaml never got it. Netlify installs with --frozen-lockfile, so the install fails before the build is reached:

ERR_PNPM_OUTDATED_LOCKFILE  Cannot install with "frozen-lockfile" because
pnpm-lock.yaml is not up to date with <ROOT>/package.json
    Failure reason: specifiers in the lockfile (...) don't match specs in package.json (...)
    the only difference is next-intl

That is why the six checks on this PR ("Header rules", "Pages changed", "Redirect rules" — the two deploy previews each report three) were failing: they report the preview failing to build, and the preview cannot build while the install is refused. It is repo-wide, not specific to this branch.

The commit adds next-intl and its dependency tree to the lockfile and nothing else — pnpm install --no-frozen-lockfile reports no specifier changes for existing packages, the 439 added lines are all entries the package needs (icu-minify, intl-messageformat, negotiator, po-parser, the SWC extractor plugin). Verified after the change:

$ pnpm install --frozen-lockfile
Already up to date          # the exact command that used to abort

$ pnpm build
…compiled successfully, full route table printed, middleware 34 kB

The dependency is real, not stale: src/i18n.ts and src/request.ts both import { getRequestConfig } from "next-intl/server".

This commit is also on the other three open PRs from the same base (#490, #491, #493) so their previews can go green independently of this one merging.

[jarik2014]

Update on the checks, since they now tell a clearer story: #492 is fully green (both deploy previews, header/redirect rules), and this one is still red — but not for the reason it was.

This branch carries the lockfile sync, so the install no longer aborts. What is left is the defects that live on main itself — the missing useEffect import in Navbar.tsx, the duplicated stepRef, the SkeletonBar prop type, the locale guard cast. They are not introduced by this PR; they are why every deploy preview in this repository fails, including this one's. #492 removes all four, which is why #492 builds.

I am deliberately not copying those fixes here: they would duplicate #492, and when it merges this branch picks them up on rebase. If you would rather each PR stand alone and be green today, say so and I will cherry-pick them in.