✨ feat(megadebrid): add API mode with toggle and provider labels

- Add Mega-Debrid API support (connectUser + getLink endpoints)
- API mode preferred by default, with automatic web fallback on failure
- User toggle "Mega-Debrid bevorzugt über API" in settings UI
- Provider labels now show source: "Mega-Debrid (API)" or "Mega-Debrid (Web)"
- sourceLabel propagated through all provider result paths
- API session token cached for 20 minutes with auto-invalidation
- Remove megaWebUnrestrict requirement for Mega-Debrid provider config

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

src/main/storage.ts

@@ -110,6 +110,7 @@ export function normalizeSettings(settings: AppSettings): AppSettings {
     realDebridUseWebLogin: Boolean(settings.realDebridUseWebLogin),
     megaLogin: asText(settings.megaLogin),
     megaPassword: asText(settings.megaPassword),
+    megaDebridPreferApi: settings.megaDebridPreferApi !== undefined ? Boolean(settings.megaDebridPreferApi) : true,
     bestToken: asText(settings.bestToken),
     allDebridToken: asText(settings.allDebridToken),
     allDebridUseWebLogin: Boolean(settings.allDebridUseWebLogin),