feat(sql): construct Postgres and Oracle providers; MySql/Odbc stay reserved

Widens the two provider gates so an authored `{"provider":"Postgres"}` or
`{"provider":"Oracle"}` binds that provider's own dialect instead of failing
"not available in this build":

- `SqlDriverFactoryExtensions.CreateDialect` gains a Postgres and an Oracle
  arm. There is deliberately no fallback arm — a default resolving to
  SqlServerDialect would construct happily and then emit T-SQL at a Postgres
  or Oracle server. The rejection message now names the three supported and
  the two still-reserved providers.
- `SqlDriverBrowser.DefaultDialectSelector` widens identically, so a provider
  the runtime constructs is also browsable; MySql/Odbc keep resolving to null
  and the caller keeps reporting them as unavailable.

Tests: the existing rejected-provider controls flip from Postgres to MySql
(factory) and Odbc (browser) so the reserved half stays falsifiable, and the
new legs assert the bound dialect TYPE rather than mere construction —
"no throw" alone would pass against a SqlServer fallback.

Doc-comment sweep (contract addition, one line each): the "v1 constructs
SqlServer only" / "reserved for P2" claims in SqlProvider, SqlDriverConfigDto,
ISqlDialect.Provider and SqlServerDialect are now false and were corrected in
the same change.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts/SqlProvider.cs

@@ -1,21 +1,25 @@
 namespace ZB.MOM.WW.OtOpcUa.Driver.Sql.Contracts;
 
-/// <summary>Which ADO.NET provider/dialect backs a Sql driver instance. v1 constructs only SqlServer.</summary>
+/// <summary>
+///     Which ADO.NET provider/dialect backs a Sql driver instance. <b>Constructed:</b> SqlServer, Postgres,
+///     Oracle — each over a fully managed provider package, no native client install. <b>Reserved:</b> MySql
+///     and Odbc are declared names only; authoring one fails at driver construction and at browse.
+/// </summary>
 public enum SqlProvider
 {
-    /// <summary>Microsoft SQL Server via <c>Microsoft.Data.SqlClient</c> — the only provider v1 constructs.</summary>
+    /// <summary>Microsoft SQL Server via <c>Microsoft.Data.SqlClient</c>.</summary>
     SqlServer,
 
-    /// <summary>PostgreSQL (Npgsql) — reserved for P2; not constructed in v1.</summary>
+    /// <summary>PostgreSQL via the managed <c>Npgsql</c> provider.</summary>
     Postgres,
 
-    /// <summary>MySQL / MariaDB — reserved; not constructed in v1.</summary>
+    /// <summary>MySQL / MariaDB — reserved; no dialect ships, so this is not constructed.</summary>
     MySql,
 
-    /// <summary>Generic ODBC — reserved for P2; not constructed in v1.</summary>
+    /// <summary>Generic ODBC — reserved; no dialect ships, so this is not constructed.</summary>
     Odbc,
 
-    /// <summary>Oracle — reserved; not constructed in v1.</summary>
+    /// <summary>Oracle Database via the fully managed <c>Oracle.ManagedDataAccess.Core</c> provider.</summary>
     Oracle,
 }