feat(sql): MySql provider over MySqlConnector, one shared provider map (lmxopcua#753)

SqlProvider.MySql is now a constructed backend instead of a reserved name.

- MySqlDialect (Driver.Sql.Dialect): MySqlConnector 2.6.2 (MIT, fully managed,
  no vulnerable packages), backtick quoting with MySQL's 64-char / no-trailing-
  space rules, information_schema catalog SQL with the database as the schema
  (system databases excluded, aliases pinned), trailing LIMIT, a type map that
  also reads the reader-side spellings (INT UNSIGNED -> UInt32, BOOL -> Boolean).
- SqlDialects: the one provider -> dialect map. The factory, the Test Connect
  probe and the browse picker each carried their own switch (and drifted once);
  they now all read this, and their refusals list the supported/reserved sets
  from it.
- AdminUI driver form offers MySql.
- Tests: MySqlDialectTests (golden quoting/catalog/type map/planner SQL); the
  provider-gate tests in factory, probe, browser and form now treat MySql as
  supported and Odbc as the reserved control. MySqlReadTests + Docker/mysql
  (throwaway mysql:8.4, SELECT-only login): liveness, KV/wide-row/topByTimestamp,
  INT keys vs authored text, case folding against case-sensitive table names,
  catalog rejection, browse walk, factory+probe, named query with a bound
  parameter, and a writing stored function whose effect the rolled-back
  transaction discards.

(lmxopcua#753)

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/SqlDriverFormContractTests.cs

@@ -101,6 +101,7 @@ public sealed class SqlDriverFormContractTests
     [InlineData(SqlProvider.SqlServer, "SqlServer")]
     [InlineData(SqlProvider.Postgres, "Postgres")]
     [InlineData(SqlProvider.Oracle, "Oracle")]
+    [InlineData(SqlProvider.MySql, "MySql")]
     public void Every_dropdown_provider_round_trips_through_the_form_model(SqlProvider provider, string name)
     {
         var form = new SqlDriverForm.FormModel { Provider = provider, ConnectionStringRef = "MesStaging" };
@@ -116,12 +117,10 @@ public sealed class SqlDriverFormContractTests
     }
 
     /// <summary>
-    ///     MySql and Odbc stay reserved-and-rejected (design §2), so the dropdown deliberately does not offer
-    ///     them. Nothing in the form model blocks the value — this records the intent so a later "the enum has
+    ///     Odbc stays reserved-and-rejected in this build, so the dropdown deliberately does not offer it. Nothing in the form model blocks the value — this records the intent so a later "the enum has
     ///     five members, the dropdown should too" edit has to argue with a test.
     /// </summary>
     [Theory]
-    [InlineData(SqlProvider.MySql)]
     [InlineData(SqlProvider.Odbc)]
     public void Reserved_providers_are_not_offered_but_still_serialize_by_name(SqlProvider reserved)
     {