feat: dynamic provider order, hoster routing, MKV sample fix

- Replace fixed primary/secondary/tertiary slots with unlimited ordered
  providerOrder: DebridProvider[] list; supports as many accounts as needed
- Provider list reorderable via up/down buttons in Accounts settings tab
- Migration: derives order from legacy primary/secondary/tertiary if empty
- Mega-Debrid split into megadebrid-api and megadebrid-web as separate providers
- Add per-hoster routing (hosterRouting) to assign specific debrid provider per hoster
- Fix duplicate MKV files in library: filter out sample files from Sample subfolders
- Remove legacy provider-selection dropdowns from hidden settings section
- Add CSS for provider-order-list/row/num/label/actions classes
- Update debrid tests: add providerOrder: [] to use legacy fallback path

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/debrid.ts

@@ -1993,11 +1993,10 @@ export class DebridService {
       }
     }
 
-    const order = toProviderOrder(
-      settings.providerPrimary,
-      settings.providerSecondary,
-      settings.providerTertiary
-    );
+    // Dynamische Reihenfolge: providerOrder hat Vorrang, Fallback auf altes primary/secondary/tertiary
+    const order: DebridProvider[] = (settings.providerOrder && settings.providerOrder.length > 0)
+      ? uniqueProviderOrder(settings.providerOrder)
+      : toProviderOrder(settings.providerPrimary, settings.providerSecondary, settings.providerTertiary);
 
     const primary = order[0];
     if (!settings.autoProviderFallback) {