feat(commons): add Audit{Channel,Kind,Status,ForwardState} enums for #23

src/ScadaLink.Commons/Types/Enums/AuditChannel.cs

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+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// Top-level Audit Log (#23) channel — the trust boundary the audited action crosses.
+/// One of: outbound API call, outbound DB write, notification send/deliver, or inbound API request.
+/// </summary>
+public enum AuditChannel
+{
+    ApiOutbound,
+    DbOutbound,
+    Notification,
+    ApiInbound
+}

src/ScadaLink.Commons/Types/Enums/AuditForwardState.cs

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+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// Site-local Audit Log (#23) forwarding state, tracked only in the site SQLite hot-path.
+/// Central rows leave this null. <c>Pending</c> = not yet sent; <c>Forwarded</c> = telemetry sent
+/// and acked; <c>Reconciled</c> = confirmed present centrally via the periodic pull fallback.
+/// The site retention purge MUST NOT drop a row whose state is still <c>Pending</c>.
+/// </summary>
+public enum AuditForwardState
+{
+    Pending,
+    Forwarded,
+    Reconciled
+}

src/ScadaLink.Commons/Types/Enums/AuditKind.cs

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+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// Specific Audit Log (#23) event kind within a channel — what action produced the row.
+/// Cached variants emit multiple rows per operation (submit → forward → attempt → resolve).
+/// See alog.md §4 for the full taxonomy.
+/// </summary>
+public enum AuditKind
+{
+    ApiCall,
+    ApiCallCached,
+    DbWrite,
+    DbWriteCached,
+    NotifySend,
+    NotifyDeliver,
+    InboundRequest,
+    InboundAuthFailure,
+    CachedSubmit,
+    CachedResolve
+}

src/ScadaLink.Commons/Types/Enums/AuditStatus.cs

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+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// Lifecycle status of an Audit Log (#23) event row.
+/// Cached operations produce multiple rows tracking <c>Submitted → Forwarded → Attempted → Delivered/Parked/Discarded</c>.
+/// <c>Skipped</c> is used when an action was short-circuited (e.g. dry-run) but should still be audited.
+/// </summary>
+public enum AuditStatus
+{
+    Submitted,
+    Forwarded,
+    Attempted,
+    Delivered,
+    Failed,
+    Parked,
+    Discarded,
+    Skipped
+}

tests/ScadaLink.Commons.Tests/Types/Enums/AuditEnumTests.cs

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+using ScadaLink.Commons.Types.Enums;
+
+namespace ScadaLink.Commons.Tests.Types.Enums;
+
+/// <summary>
+/// Asserts the exact member sets of the Audit Log (#23) enums.
+/// Lock-in tests; any addition/removal/rename is a deliberate design change
+/// that must come with a corresponding update to alog.md §4.
+/// </summary>
+public class AuditEnumTests
+{
+    [Fact]
+    public void AuditChannel_HasExactlyExpectedMembers()
+    {
+        var expected = new[] { "ApiOutbound", "DbOutbound", "Notification", "ApiInbound" };
+        var actual = Enum.GetValues(typeof(AuditChannel))
+            .Cast<AuditChannel>()
+            .Select(x => x.ToString())
+            .ToArray();
+
+        Assert.Equal(expected.Length, actual.Length);
+        Assert.Equal(expected, actual);
+    }
+
+    [Fact]
+    public void AuditKind_HasExactlyTenExpectedMembers()
+    {
+        var expected = new[]
+        {
+            "ApiCall", "ApiCallCached", "DbWrite", "DbWriteCached",
+            "NotifySend", "NotifyDeliver", "InboundRequest", "InboundAuthFailure",
+            "CachedSubmit", "CachedResolve",
+        };
+        var actual = Enum.GetValues(typeof(AuditKind))
+            .Cast<AuditKind>()
+            .Select(x => x.ToString())
+            .ToArray();
+
+        Assert.Equal(10, actual.Length);
+        Assert.Equal(expected, actual);
+    }
+
+    [Fact]
+    public void AuditStatus_HasExactlyEightExpectedMembers()
+    {
+        var expected = new[]
+        {
+            "Submitted", "Forwarded", "Attempted", "Delivered",
+            "Failed", "Parked", "Discarded", "Skipped",
+        };
+        var actual = Enum.GetValues(typeof(AuditStatus))
+            .Cast<AuditStatus>()
+            .Select(x => x.ToString())
+            .ToArray();
+
+        Assert.Equal(8, actual.Length);
+        Assert.Equal(expected, actual);
+    }
+
+    [Fact]
+    public void AuditForwardState_HasExactlyExpectedMembers()
+    {
+        var expected = new[] { "Pending", "Forwarded", "Reconciled" };
+        var actual = Enum.GetValues(typeof(AuditForwardState))
+            .Cast<AuditForwardState>()
+            .Select(x => x.ToString())
+            .ToArray();
+
+        Assert.Equal(expected.Length, actual.Length);
+        Assert.Equal(expected, actual);
+    }
+}