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.

tests/api/admin-settings-core.routes.test.ts

@@ -152,8 +152,8 @@ describe('Admin settings core routes', () => {
   it('rejects invalid download client types', async () => {
     const request = {
       json: vi.fn().mockResolvedValue({
-        type: 'transmission',
-        url: 'http://transmission',
+        type: 'deluge',
+        url: 'http://deluge',
       }),
     };