Fix Lite Overview ghost-line comparison offset under a preset range (#4296)

[erikdarlingdata]

Closes #4296.

Why

Lite's Overview tab has a "Compare to" ghost-line overlay on the correlated timeline lanes (CPU, waits,
blocking, memory, file I/O). ServerTab.RefreshOverviewAsync builds the reference (ghost-line) time
window and hands it to CorrelatedTimelineLanesControl.RefreshAsync, which reads it straight into
LocalDataService.GetCpuUtilizationAsync, GetTotalWaitTrendAsync, and friends. Those reads treat a
supplied fromDate/toDate as the monitored server's own local time, not UTC.

Under a PRESET range (no custom dates picked), the window was built from DateTime.UtcNow instead of the
server's local now. On a server not on UTC, the reads got a window shifted by the server's offset. The
ghost line came from the wrong hours entirely, not just a display skew. The same raw DateTime.UtcNow
fallback was duplicated in two more places: RefreshAsync's timeShift (the ghost line's X-axis
alignment) and ComparisonLabel (the "yesterday" / "last week" text). So even after fixing the reference
window alone, the overlay stayed misplaced on the chart and mislabeled. A CUSTOM range was already correct:
the date pickers convert to server time before RefreshOverviewAsync ever sees fromDate/toDate.

The three call sites are RefreshOverviewAsync, RefreshAsync's timeShift and ComparisonLabel. With the
two changed files reverted to this branch's parent commit, the new source pin test failed.

The Darling viewer has no ghost-line overlay to fix in parallel. Its
CorrelatedTimelineLanesControl.xaml.cs header says so directly: "Deliberately dropped for v1 (noted in
the PR): Lite's comparison-range ghost-line overlay (the whole comparisonRange block, AddGhostLine,
ComparisonLabel)."

What changes

• Lite/Controls/CorrelatedTimelineLanesControl.xaml.cs: two new internal static helpers,
  GetCurrentWindowServerLocal and GetOverviewComparisonRange. Under a preset range, they build the
  current window from the server's own local now: utcNow.AddMinutes(utcOffsetMinutes). That is the result
  ServerTimeHelper.ToServerTime gives, without its static state. Under a custom
  range they pass the already-server-local fromDate/toDate through unchanged. GetOverviewComparisonRange
  returns CurrentFrom with From and To. So RefreshAsync's timeShift and ComparisonLabel use the
  same current-window start that the reference range came from. Before, each one read DateTime.UtcNow again. That makes the shift exact arithmetic
  (currentStart - (currentStart - N days) = N days) instead of two independent clock reads a network
  round-trip apart.
• Lite/Controls/ServerTab.Refresh.cs: RefreshOverviewAsync now calls
  CorrelatedTimelineLanesControl.GetOverviewComparisonRange instead of the shared
  ServerTab.Comparison.cs GetComparisonRange(). Under a preset range, that shared helper falls
  back to UTC. That is right for the Queries-tab comparisons it also serves, because they read the UTC
  collection_time directly. It is wrong for the correlated lanes. So the Overview tab gets its own
  derivation, and the Queries tab keeps the shared one.
• Lite.Tests/OverviewComparisonWindowOffsetTests.cs (new) pins both helpers for a server at UTC+5 and one
  at UTC-7, under a preset and a custom range. A source pin also checks the three call sites.
• Filed Dashboard: Overview ghost-line comparison likely has the same UTC-offset bug as Lite (#4296) #4305 to check whether the deprecated Dashboard app's byte-for-byte
  copy of this control (deprecated/Dashboard/Controls/CorrelatedTimelineLanesControl.xaml.cs, flagged by
  its own "SYNC WARNING" header) has the same bug. Not fixed here: Dashboard is a separate, SQL-Server-only
  product with its own data service. Confirming the same UTC-vs-server-local read semantics apply there
  needs its own look, not a copy-paste of this fix.

This branch also merges in #4302 (#4284's Queries-tab fix), which landed on dev while this PR was in
progress and touched the same RefreshOverviewAsync method. Its own comment there named #4296 as the
mismatch it did not fix. The merge conflict was resolved by keeping this PR's derivation, which supersedes
that comment.

Test plan

• dotnet build Lite.Tests/Lite.Tests.csproj -c Debug: 0 Warning(s), 0 Error(s), both before and
  after merging origin/dev.
• Lite.Tests.exe -class "PerformanceMonitorLite.Tests.OverviewComparisonWindowOffsetTests": 9/9
  passed.
• The source pin fails on the old code. The parent commit's copies of both files still have the old
  DateTime.UtcNow lines and lack the new ones.
• Full suite after merging origin/dev, Lite.Tests.exe with no filter: Total 5398, Errors 0,
  Failed 0, Skipped 0, Not Run 0.
• GitHub Actions CI on 66b3a337: build, Darling PostgreSQL tests and Lite tests all pass.

CHANGELOG entry

SECTION: Fixed
ENTRY:

• Lite's Overview ghost line reads the right hours outside UTC ([Fix Lite Overview ghost-line comparison offset under a preset range (#4296) #4309]) - Under a preset time range,
  the "Compare to" ghost line read a window off by the server's UTC offset. So on a server not set to UTC,
  it covered the wrong hours of the day it compared against. The window, the line's position
  and its label now all come from the server's local time.
  REF:
  [Fix Lite Overview ghost-line comparison offset under a preset range (#4296) #4309]: Fix Lite Overview ghost-line comparison offset under a preset range (#4296) #4309

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