refactor(historian): extract Driver.Historian.Sql.Common from the SQL Server backend (no behaviour change) (1a)

Moves the database-independent logic of the SQL Server historian backend into a new
shared library for the upcoming QuestDB backend (#666): status codes and bits, value/column
mapping, StoredSample + quality clamp, the AtTime and aggregate evaluators, BucketPlan,
LiveWritePreparer and HistoryUpdatePlanner (both with a resolutionTicks parameter, default 1),
tag-name rules, the bootstrap failure cache, health counters, alarm event ids, the event
continuation and severity clamp. The SQL Server backend now calls it; its T-SQL, TVP
builders, connection, bootstrapper and catalog stay.

Tests: StatusCodeOracleTests, ValueWriterPrepareTests, the column half of SampleRowMapperTests
and ProcessedReadTests.Every_enum_member_is_either_served_or_refused move to the new
Sql.Common.Tests under the same names. SqlServer integration tests get mechanical renames
only. Test-name set across the three projects is identical to the baseline (160 tests).

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common/BucketRow.cs

@@ -0,0 +1,57 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common;
+
+/// <summary>
+///     Per-bucket statistics one aggregate query row produces (one non-empty bucket). Every backend's SQL fills the same
+///     fields; <see cref="AggregateEvaluator"/> turns them into the OPC UA value and status.
+/// </summary>
+/// <remarks>
+///     Sample classes: <i>usable</i> = severity Good or Uncertain AND a stored value (an Empty sample is an outage marker
+///     and counts as Bad whatever its code); <i>good</i> = usable with severity Good; <i>bad</i> = not usable.
+///     Every value field is computed over usable samples only.
+/// </remarks>
+public sealed class BucketRow
+{
+    /// <summary>Zero-based bucket index within the window.</summary>
+    public long Bucket { get; set; }
+
+    /// <summary>All samples in the bucket.</summary>
+    public int Total { get; set; }
+
+    /// <summary>Usable samples.</summary>
+    public int Usable { get; set; }
+
+    /// <summary>Good samples.</summary>
+    public int Good { get; set; }
+
+    /// <summary>Bad (not usable) samples.</summary>
+    public int Bad { get; set; }
+
+    /// <summary>Usable String / DateTime samples.</summary>
+    public int NonNumeric { get; set; }
+
+    /// <summary>Average of the usable numeric values (null when none).</summary>
+    public double? Avg { get; set; }
+
+    /// <summary>Minimum of the usable numeric values (null when none).</summary>
+    public double? Min { get; set; }
+
+    /// <summary>Maximum of the usable numeric values (null when none).</summary>
+    public double? Max { get; set; }
+
+    /// <summary>Sum of the usable numeric values (null when none).</summary>
+    public double? Sum { get; set; }
+
+    /// <summary>First usable sample's value by time (Empty when none).</summary>
+    public HistorianValue First { get; set; }
+
+    /// <summary>Last usable sample's value by time (Empty when none).</summary>
+    public HistorianValue Last { get; set; }
+
+    /// <summary>Extreme (min or max) usable numeric value (null when none).</summary>
+    public double? Extreme { get; set; }
+
+    /// <summary>Time of <see cref="Extreme"/> (ties ⇒ earliest; null when none).</summary>
+    public DateTime? ExtremeTime { get; set; }
+}