feat: default pla filaments

backend/src/main/java/com/printcalculator/controller/OptionsController.java

@@ -65,6 +65,20 @@ public class OptionsController {
                 .filter(m -> m != null)
                 .collect(Collectors.toList());
         
+        // Sort: PLA first, then PETG, then others alphabetically
+        materialOptions.sort((a, b) -> {
+            String codeA = a.code();
+            String codeB = b.code();
+            
+            if (codeA.equals("pla_basic")) return -1;
+            if (codeB.equals("pla_basic")) return 1;
+            
+            if (codeA.equals("petg_basic")) return -1;
+            if (codeB.equals("petg_basic")) return 1;
+            
+            return codeA.compareTo(codeB);
+        });
+
         // 2. Qualities (Static as per user request)
         List<OptionsResponse.QualityOption> qualities = List.of(
                 new OptionsResponse.QualityOption("draft", "Draft"),

frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts

@@ -112,7 +112,9 @@ export class UploadFormComponent implements OnInit {
   private setDefaults() {
       // Set Defaults if available
       if (this.materials().length > 0 && !this.form.get('material')?.value) {
-           this.form.get('material')?.setValue(this.materials()[0].value);
+           // Prefer PLA Basic, otherwise first available
+           const pla = this.materials().find(m => m.value === 'pla_basic');
+           this.form.get('material')?.setValue(pla ? pla.value : this.materials()[0].value);
       }
       if (this.qualities().length > 0 && !this.form.get('quality')?.value) {
           // Try to find 'standard' or use first