Add Transmission/NZBGet and per-client paths and much more

Extend multi-download-client support to include Transmission and NZBGet and introduce per-client custom download paths. Adds protocol mapping and new client types, Transmission/NZBGet integration services, API CRUD and validation changes, UI components/modal updates and live path previews, and manager routing by protocol. Includes DB migrations (download_path on download_history, interactive_search_access on users), schema updates, and related processor/service fixes and tests to ensure backward compatibility and proper path resolution.

prisma/schema.prisma

@@ -53,6 +53,9 @@ model User {
   // Request approval preferences
   autoApproveRequests Boolean? @map("auto_approve_requests") // null = use global setting, true = auto-approve, false = require approval
 
+  // Fine-grained permissions
+  interactiveSearchAccess Boolean? @map("interactive_search_access") // null = use global setting, true = allow, false = deny
+
   // Soft delete support
   deletedAt DateTime? @map("deleted_at")
   deletedBy String?   @map("deleted_by") // Admin user ID who deleted this user
@@ -275,6 +278,7 @@ model DownloadHistory {
   downloadStatus   String?   @map("download_status")
   // Status values: queued, downloading, completed, failed, stalled
   downloadError    String?   @map("download_error") @db.Text
+  downloadPath     String?   @map("download_path") @db.Text
   startedAt        DateTime? @map("started_at")
   completedAt      DateTime? @map("completed_at")
   createdAt        DateTime  @default(now()) @map("created_at")