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.SqlBreakdown/Classes/SqlBreakdownBase.cs

@@ -48,6 +48,18 @@ public abstract class SqlBreakdownBase : ISqlBreakdown
     /// </summary>
     public bool IsUsingFinishClause => FinishClauses.Count > 0;
 
+    /// <summary>
+    /// Re-establishes the invariants normally guaranteed by the constructors after the object
+    /// is reconstructed by deserialization. Deserialization bypasses constructors, so the
+    /// collection state must be re-validated to avoid a partially-initialized object
+    /// (SonarQube rule S5766).
+    /// </summary>
+    protected void RevalidateBreakdownState()
+    {
+        SetupClauses ??= new List<string>();
+        FinishClauses ??= new ArrayList();
+    }
+
     /// <summary>
     /// Gets the SQL breakdown as a string. Must be implemented by derived classes.
     /// </summary>