fix(migrations): support Closure-based 'up'/'down' in MigrationRunner

The runner was calling splitStatements(string) directly on migration['up']
without checking whether it was a Closure, causing a fatal type error on
all idempotent closure-based migrations (Phase_94_001, _002, Phase_96_001).
Now checks is_callable() first and invokes the closure, falling back to
string SQL splitting for plain-string migrations.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Core/Migration/MigrationRunner.php

@@ -38,11 +38,15 @@ final class MigrationRunner
 
                 if (is_array($migration) && isset($migration['up'])) {
                     $upSql = $migration['up'];
-                    $statements = $this->splitStatements($upSql);
-                    foreach ($statements as $stmt) {
-                        $stmt = trim($stmt);
-                        if ($stmt !== '') {
-                            $this->db->raw($stmt);
+                    if (is_callable($upSql)) {
+                        $upSql($this->db);
+                    } else {
+                        $statements = $this->splitStatements((string) $upSql);
+                        foreach ($statements as $stmt) {
+                            $stmt = trim($stmt);
+                            if ($stmt !== '') {
+                                $this->db->raw($stmt);
+                            }
                         }
                     }
                 } elseif (is_object($migration) && method_exists($migration, 'up')) {
@@ -93,11 +97,16 @@ final class MigrationRunner
                     $migration = require $file;
 
                     if (is_array($migration) && isset($migration['down'])) {
-                        $statements = $this->splitStatements($migration['down']);
-                        foreach ($statements as $stmt) {
-                            $stmt = trim($stmt);
-                            if ($stmt !== '') {
-                                $this->db->raw($stmt);
+                        $downSql = $migration['down'];
+                        if (is_callable($downSql)) {
+                            $downSql($this->db);
+                        } else {
+                            $statements = $this->splitStatements((string) $downSql);
+                            foreach ($statements as $stmt) {
+                                $stmt = trim($stmt);
+                                if ($stmt !== '') {
+                                    $this->db->raw($stmt);
+                                }
                             }
                         }
                     } elseif (is_object($migration) && method_exists($migration, 'down')) {