chore(web): remove reduced-availability banner from usage page

[pandemicsyn]

Summary

Removes the "Usage currently has reduced availability. Check the status page for
updates." warning banner from the usage page. The banner was tied to a past
status-page incident and is no longer wanted on the dashboard.

• Deleted the <UsageAvailabilityBanner /> render (and its import) from
  UsageAnalyticsDashboard.tsx; no other code paths referenced the banner.
• Kept the UsageAvailabilityBanner component file in place so the banner can
  be re-enabled with a one-line change if a similar incident recurs.

Verification

• No manual verification was performed in this session: the change is a render
  removal in one file, and the sandboxed environment could not run the web app
  or a browser to exercise the usage page.
• Verify the usage page renders normally (no banner, no layout gap) in a
  preview deployment.

Visual Changes

Before	After
Usage page shows warning banner: "Usage currently has reduced availability. Check the status page for updates."	Banner no longer rendered; page content starts directly with the Usage heading

Reviewer Notes

• Small, mechanical diff: one file, 3 deleted lines, no logic changes.
• isSalesDemo remains used elsewhere in the dashboard, so no unused-variable
  fallout from removing its use in the banner condition.
• Re-enabling later is trivial: restore the component import and the
  {!isSalesDemo && <UsageAvailabilityBanner />} line.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 files)

• apps/web/src/components/usage-analytics/UsageAnalyticsDashboard.tsx

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_{Review guidance: REVIEW.md from base branch main}