fix(downloads): harden recovery, replacement, and cleanup

- make media credential recovery durable and explicit across lifecycle entry points
- protect exact output replacement with platform-aware ownership, fingerprints, locks, and crash-safe quarantine
- permanently remove unfinished assets while preserving safe completed and Torrent cleanup
- add frontend, native, and localization regressions

src/utils/downloads.ts

@@ -788,6 +788,16 @@ const persistableRequestHeaders = (headers: string | null | undefined): string |
   return lines.length > 0 ? lines.join('\n') : undefined;
 };
 
+/**
+ * Preserve only stable, non-credential request context for an explicit
+ * credentialless retry. This uses the same allow-list and URL sanitization as
+ * persistence so a retry cannot accidentally reuse a signed Referer or an
+ * unknown token-bearing header.
+ */
+export const headersWithoutCredentialMaterial = (
+  headers: string | null | undefined
+): string | undefined => persistableRequestHeaders(headers);
+
 /**
  * Returns a shallow copy of `item` with secret fields removed. Volatile
  * progress fields (`fraction`, `speed`, `eta`) are also dropped as in the