feat(audit): M5.3 response-capture increments — request headers, ceiling-hits counter, per-method body opt-out (T7)

1. Request headers in Extra JSON (AuditWriteMiddleware): adds a `requestHeaders`
   object to the existing Extra JSON alongside remoteIp/userAgent; headers whose
   names appear in AuditLogOptions.HeaderRedactList (Authorization, X-Api-Key,
   Cookie, Set-Cookie by default) are replaced with "<redacted>" using
   OrdinalIgnoreCase matching — same policy as ScadaBridgeAuditRedactor.

2. AuditInboundCeilingHits counter: new IAuditInboundCeilingHitsCounter interface
   + NoOpAuditInboundCeilingHitsCounter default; AuditCentralHealthSnapshot
   implements the interface (Interlocked field, thread-safe) and exposes
   AuditInboundCeilingHits on IAuditCentralHealthSnapshot; AddAuditLog registers
   the NoOp default, AddAuditLogCentralMaintenance forwards to the snapshot;
   AuditWriteMiddleware accepts the counter as an optional ctor arg and increments
   it once per request where either the request or response body hit the cap.

3. Per-method SkipBodyCapture opt-out: adds SkipBodyCapture bool to
   PerTargetRedactionOverride; AuditWriteMiddleware consults the per-target
   override map at the start of InvokeAsync (before EnableBuffering) and, when
   set, skips body read + capture entirely — the audit row still emits with
   headers/metadata but null RequestSummary/ResponseSummary; truncation flags
   are also cleared so the ceiling-hits counter is not bumped for opted-out methods.

src/ZB.MOM.WW.ScadaBridge.AuditLog/Central/AuditCentralHealthSnapshot.cs

@@ -39,10 +39,12 @@ namespace ZB.MOM.WW.ScadaBridge.AuditLog.Central;
 public sealed class AuditCentralHealthSnapshot
     : IAuditCentralHealthSnapshot,
       ICentralAuditWriteFailureCounter,
-      IAuditRedactionFailureCounter
+      IAuditRedactionFailureCounter,
+      IAuditInboundCeilingHitsCounter
 {
     private int _centralAuditWriteFailures;
     private int _auditRedactionFailure;
+    private int _auditInboundCeilingHits;
     private readonly ConcurrentDictionary<string, bool> _stalled = new();
 
     /// <inheritdoc/>
@@ -53,6 +55,10 @@ public sealed class AuditCentralHealthSnapshot
     public int AuditRedactionFailure =>
         Interlocked.CompareExchange(ref _auditRedactionFailure, 0, 0);
 
+    /// <inheritdoc/>
+    public int AuditInboundCeilingHits =>
+        Interlocked.CompareExchange(ref _auditInboundCeilingHits, 0, 0);
+
     /// <inheritdoc/>
     public IReadOnlyDictionary<string, bool> SiteAuditTelemetryStalled =>
         new Dictionary<string, bool>(_stalled);
@@ -78,4 +84,8 @@ public sealed class AuditCentralHealthSnapshot
     /// <inheritdoc/>
     void IAuditRedactionFailureCounter.Increment() =>
         Interlocked.Increment(ref _auditRedactionFailure);
+
+    /// <inheritdoc/>
+    void IAuditInboundCeilingHitsCounter.Increment() =>
+        Interlocked.Increment(ref _auditInboundCeilingHits);
 }