fix(pgsql): strip backticks from column defaults in migration paths

Backtick-wrapped defaults (e.g. from GORM tags like `now()`) were only
stripped in the CREATE TABLE column-definition path, leaving raw
backticks in the ALTER COLUMN ... SET DEFAULT migration statement and
in the migration-generated CREATE TABLE template, producing invalid
SQL. Default-drift comparisons also compared raw values, so a
backtick-wrapped model default never matched the live DB default and
kept re-emitting redundant ALTER statements.

pkg/writers/pgsql/migration_writer.go

@@ -460,7 +460,7 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 			}
 
 			// Check default value changes
-			if fmt.Sprintf("%v", modelCol.Default) != fmt.Sprintf("%v", currentCol.Default) {
+			if !columnDefaultsEqual(modelCol.Default, currentCol.Default) {
 				setDefault, defaultVal := formatColumnDefaultSQL(modelCol)
 
 				sql, err := w.executor.ExecuteAlterColumnDefaultWithCheck(AlterColumnDefaultWithCheckData{
@@ -956,7 +956,24 @@ func columnsEqual(col1, col2 *models.Column) bool {
 	}
 	return columnTypesEqual(col1, col2) &&
 		col1.NotNull == col2.NotNull &&
-		fmt.Sprintf("%v", col1.Default) == fmt.Sprintf("%v", col2.Default)
+		columnDefaultsEqual(col1.Default, col2.Default)
+}
+
+// columnDefaultsEqual compares column defaults for drift detection, stripping
+// MySQL-style backticks (e.g. from GORM tags) so a model default of
+// "`now()`" is recognised as equal to a live default of "now()".
+func columnDefaultsEqual(default1, default2 interface{}) bool {
+	return normalizeDefaultForCompare(default1) == normalizeDefaultForCompare(default2)
+}
+
+func normalizeDefaultForCompare(value interface{}) string {
+	if value == nil {
+		return ""
+	}
+	if s, ok := value.(string); ok {
+		return strings.TrimSpace(stripBackticks(s))
+	}
+	return fmt.Sprintf("%v", value)
 }
 
 func columnTypesEqual(col1, col2 *models.Column) bool {