fix(security): Resolve SonarQube security hotspots

Introduce a default regex match timeout across the library to prevent potential ReDoS attacks (SonarQube rule S6444).
Implement `[OnDeserialized]` methods to re-establish object invariants and validate state after deserialization, addressing SonarQube rule S5766.

src/Strata.SqlTools.PostgreSql/Breakdowns/QueryBreakdown.cs

@@ -1,4 +1,5 @@
 using System.Collections;
+using System.Runtime.Serialization;
 using Strata.SqlTools.SqlBreakdown.Expressions;
 using Strata.SqlTools.SqlBreakdown.Interfaces.Core;
 using CommandVisitor = Strata.SqlTools.Visitors.PostgreSql.CommandVisitor;
@@ -88,6 +89,14 @@ public class QueryBreakdown : SqlServerQueryBreakdown
         }
     }
 
+    /// <summary>
+    /// Re-establishes invariants after deserialization, since deserialization bypasses the
+    /// constructors that normally initialize the breakdown's clause state (SonarQube rule S5766).
+    /// </summary>
+    /// <param name="context">The streaming context for the deserialization operation.</param>
+    [OnDeserialized]
+    private void OnDeserialized(StreamingContext context) => RevalidateBreakdownState();
+
     /// <summary>
     /// Adds a parameter to the query using PostgreSQL's positional parameter format ($1, $2, ...).
     /// </summary>

src/Strata.SqlTools.PostgreSql/Breakdowns/QueryBreakdownCollection.cs

@@ -1,3 +1,4 @@
+using System.Runtime.Serialization;
 using System.Text;
 using Strata.SqlTools.SqlBreakdown.Classes;
 using Strata.SqlTools.SqlBreakdown.Interfaces;
@@ -35,6 +36,20 @@ public class QueryBreakdownCollection : SqlBreakdownCollection
         _queryBreakdowns = queryBreakdowns?.ToList() ?? new List<QueryBreakdown>();
     }
 
+    /// <summary>
+    /// Validates that the backing list survived deserialization, since deserialization bypasses
+    /// the constructors that normally initialize it (SonarQube rule S5766).
+    /// </summary>
+    /// <param name="context">The streaming context for the deserialization operation.</param>
+    [OnDeserialized]
+    private void OnDeserialized(StreamingContext context)
+    {
+        if (_queryBreakdowns is null)
+        {
+            throw new SerializationException("Deserialized QueryBreakdownCollection is missing its backing list.");
+        }
+    }
+
     /// <summary>
     /// Gets the collection of QueryBreakdown objects.
     /// </summary>