Fix non-urgent toast inline link being invisible on light theme

[999purple999]

Fixes #33494.

cc @t3chguy since you're the most recent committer to _NonUrgentToastContainer.pcss.

The bug

In light theme, the requests inline link inside the Your server isn't responding to some requests toast is invisible — the text collapses into the toast's background.

Root cause

apps/web/res/css/structures/_NonUrgentToastContainer.pcss hard-codes the container's background to #17191c and its base text colour to #fff, with an explicit comment:

/* We don't use variables on the colours because we want it to be the same */
/* in all themes. */
background-color: #17191c;
color: #fff;

So the container is always dark, in every theme. But the inline requests link is rendered as AccessibleButton kind="link_inline", whose colour rule in apps/web/res/css/views/elements/_AccessibleButton.pcss is:

&.mx_AccessibleButton_kind_link,
&.mx_AccessibleButton_kind_link_inline {
    color: var(--cpd-color-text-primary);
}

--cpd-color-text-primary is theme-dependent. In light theme it resolves to a dark colour. Dark text on #17191c is effectively invisible — that is the bug.

The fix

Pin the inline-link colour to #fff inside .mx_NonUrgentToastContainer_toast, so it follows the container's intentional theme-independent styling. The fix is scoped to the container and the specific link_inline kind, so it cannot leak outside the non-urgent toasts and it does not affect any other inline links elsewhere in the app.

.mx_NonUrgentToastContainer_toast {
    /* ... existing ... */

    .mx_AccessibleButton.mx_AccessibleButton_kind_link_inline {
        color: #fff;
    }
}

+10 LOC including the explanatory comment.

Verification

• Pure CSS change, no behaviour change outside .mx_NonUrgentToastContainer_toast.
• Selector specificity: .mx_NonUrgentToastContainer .mx_NonUrgentToastContainer_toast .mx_AccessibleButton.mx_AccessibleButton_kind_link_inline (0,4,0) overrides the upstream &.mx_AccessibleButton_kind_link_inline (0,2,0) — no !important needed.
• Manual visual confirmation against the issue screenshot: the dark toast is unchanged, the previously-invisible requests link now shows white.
• No new tests added (visual-only change, no logic).

[CLAassistant]

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