Fix sqlExecDiscardResult to use Decoders.noResult instead of rowsAffected

sqlExecDiscardResult was delegating to sqlExec which uses
sqlExecHasqlCount (Decoders.rowsAffected). This fails for SQL commands
like SET CONSTRAINTS ... DEFERRED that don't return a row count in their
command tag, causing UnexpectedResultStatementError "Empty bytes".

Now delegates to sqlExecHasql which uses Decoders.noResult instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mpscholten

ihp/IHP/ModelSupport.hs

@@ -300,8 +300,9 @@ sqlExec theQuery theParameters = do
 -- > sqlExecDiscardResult "CREATE TABLE users ()" ()
 sqlExecDiscardResult :: (?modelContext :: ModelContext, ToSnippetParams q) => Query -> q -> IO ()
 sqlExecDiscardResult theQuery theParameters = do
-    _ <- sqlExec theQuery theParameters
-    pure ()
+    let pool = ?modelContext.hasqlPool
+    let snippet = sqlToSnippet (fromQuery theQuery) (toSnippetParams theParameters)
+    sqlExecHasql pool snippet
 {-# INLINABLE sqlExecDiscardResult #-}