feat(auditlog): AuditLogPartitionMaintenanceService monthly roll-forward (#23 M6)

src/ScadaLink.AuditLog/Central/AuditLogPartitionMaintenanceOptions.cs

@@ -0,0 +1,37 @@
+namespace ScadaLink.AuditLog.Central;
+
+/// <summary>
+/// Tuning knobs for the central
+/// <see cref="AuditLogPartitionMaintenanceService"/> hosted service (M6-T5).
+/// Defaults: once every 24 hours, keep at least one future monthly
+/// boundary ahead of <see cref="DateTime.UtcNow"/>.
+/// </summary>
+/// <remarks>
+/// <para>
+/// The hosted service drives a daily roll-forward of
+/// <c>pf_AuditLog_Month</c>: each tick reads the current max boundary and
+/// SPLITs new monthly boundaries until at least
+/// <see cref="LookaheadMonths"/> future months are covered. The 1-month
+/// default is intentionally conservative — anything less risks an
+/// end-of-month race where inserts land in the unbounded tail partition;
+/// anything more wastes nothing but represents premature commitment.
+/// </para>
+/// <para>
+/// The 24-hour cadence is the cheapest interval that still guarantees
+/// at-most-one missed boundary in steady state (even a hard failover the
+/// hosted service can recover on its very next tick). Lowering this below
+/// an hour would generate more metadata churn than it saves.
+/// </para>
+/// </remarks>
+public sealed class AuditLogPartitionMaintenanceOptions
+{
+    /// <summary>Period of the maintenance tick in seconds (default 86 400 = 24 h).</summary>
+    public int IntervalSeconds { get; set; } = 86_400;
+
+    /// <summary>
+    /// Minimum number of future months that <c>pf_AuditLog_Month</c> must
+    /// cover after each tick. Default 1 — i.e. as of mid-May the partition
+    /// for the next full month (June) must already be present.
+    /// </summary>
+    public int LookaheadMonths { get; set; } = 1;
+}