i18n CreatePanel with genre picker, model selector, EditableSlider, and LoRA panel

Phase 4.3: Largest component change. Adds cascading genre picker using
Phase 3 style data, DiT model selector with backend sync, EditableSlider
for all numeric parameters, LoRA load/unload panel, bulk generate, vocal
gender selector. Batch size max kept at 4 (not 8), inference steps max
kept at 32 (not 200) to prevent OOM. Added LoRA API stubs to api.ts.
Added ditModel to GenerationParams type.

types.ts

@@ -59,6 +59,7 @@ export interface GenerationParams {
   lyrics: string;
   style: string;
   title: string;
+  ditModel?: string;
 
   // Common
   instrumental: boolean;