Add updateExisting option to importers & UI

Introduce an updateExisting flag across importers and the Importer UI to control whether existing items should be updated or only new items imported. Changes: added updateExisting to XBVR, StashAPP, Playnite, and Jellyfin config types; added checkboxes in ImporterView (enabled by default) to toggle the behavior; import logic now skips existing items when updateExisting is false and logs/skips appropriately (XBVR, StashAPP, Playnite, Jellyfin). Also: minor Playnite env parsing tweak for port (undefined when not provided) and small logging/cleanup in the Jellyfin album handling.

src/lib/xbvrImporter.ts

@@ -6,6 +6,7 @@ import { SOURCE_CATEGORY_MAPPING } from '@/types';
 export interface XBVRConfig {
   url: string;
   apiKey?: string;
+  updateExisting?: boolean;
 }
 
 export interface ImportProgress {
@@ -258,11 +259,14 @@ export async function importFromXBVR(
 
       // Check for duplicate
       if (existingTitles.has(video.title)) {
-        logCallback(`⊘ Skipped duplicate: ${video.title}`);
-        progressCallback({
-          current: uniqueActors.length + i + 1
-        });
-        continue;
+        if (!config.updateExisting) {
+          logCallback(`⊘ Skipped duplicate: ${video.title} (updateExisting is false)`);
+          progressCallback({
+            current: uniqueActors.length + i + 1
+          });
+          continue;
+        }
+        logCallback(`→ Updating existing: ${video.title}`);
       }
 
       try {