Adds the filter bar for the central Audit Log page (#23 M7-T2):
* AuditQueryModel — UI binding model with chip-style multi-select state for
Channel/Kind/Status/Site, a Channel→Kind narrowing map (CachedSubmit and
CachedResolve appear under both ApiOutbound and DbOutbound per
Component-AuditLog.md §4), time-range presets (5min/1h/24h/Custom),
free-text Instance/Script/Target/Actor searches and an Errors-only toggle.
Collapses to the single-value AuditLogQueryFilter on ToFilter(utcNow);
multi-select chips take the first selected per dimension and the
Errors-only toggle pins Failed when Status chips are empty (chip-set wins
otherwise) — documented Bundle B scope decision.
* AuditFilterBar.razor + .razor.cs — Blazor Server component (Bootstrap
only, no third-party UI libs). Renders the 10 spec elements plus the
Errors-only toggle, populates Site chips from ISiteRepository at
initialisation, exposes [Parameter] EventCallback<AuditLogQueryFilter>
OnFilterChanged and an optional NowUtcProvider seam for time-window tests.
* AuditFilterBarTests — 5 bUnit tests pinning element presence, Apply
callback payload, Channel→Kind narrowing, Errors-only toggle precedence
and the LastHour time-window collapse.
