Advance existing requests from Interactive Search

Pass requestId and requestedByUserId through request list and card components and into AudiobookDetailsModal. Add ADVANCEABLE_FROM_INTERACTIVE_SEARCH constant and logic so the Interactive Search modal routes to /api/requests/[id]/select-torrent for own/admin advanceable requests instead of creating a new request. Fix download-token usage to use the in-flight request id, extend Audiobook type with requestedByUserId, and add tests covering advance-vs-create routing and select-torrent behavior.

src/lib/hooks/useAudiobooks.ts

@@ -31,6 +31,7 @@ export interface Audiobook {
   isRequested?: boolean;  // Set if ANY user has requested this audiobook
   requestStatus?: string | null;  // Status of request (if any)
   requestId?: string | null;  // ID of request (if any)
+  requestedByUserId?: string | null;  // User id who requested (populated by audiobook-matcher; used to gate own-request interactive-search routing)
   requestedByUsername?: string | null;  // Username who requested (only if not current user)
   hasReportedIssue?: boolean;  // True if an open issue exists for this audiobook
   isIgnored?: boolean;  // True if this user has ignored this audiobook from auto-requests