feat: add per-hoster provider routing (Hoster-Zuordnung)

- New settings field hosterRouting maps file hosters to specific debrid providers
- 27 known hosters predefined (Rapidgator, Uploaded, Turbobit, Nitroflare, etc.)
- Custom hoster support via prompt dialog
- Routing takes priority over default provider chain
- Falls back to normal chain on error when autoProviderFallback is enabled
- Logs routing decisions: "Hoster-Zuordnung: rapidgator → Debrid-Link"
- Full UI section in settings with add/remove/change provider per hoster
- Storage validation and normalization for hosterRouting

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

src/main/constants.ts

@@ -98,6 +98,7 @@ export function defaultSettings(): AppSettings {
     columnOrder: ["name", "size", "progress", "hoster", "account", "prio", "status", "speed"],
     extractCpuPriority: "high",
     autoExtractWhenStopped: true,
-    disabledProviders: []
+    disabledProviders: [],
+    hosterRouting: {}
   };
 }