fix: remediate audited defects (resolves #29, #30, #31, #32)

- Fix permanent qBittorrent fallback degradation by resetting fallback flags during group-by polling (resolves #29)
- Fix Ombi webhook key mismatch in status endpoint and test mocks (resolves #30)
- Prevent timingSafeEqual TypeErrors on multi-byte CSRF token length mismatches (resolves #31)
- Eliminate duplicate write stream on server.log by delegating to index.js console override (resolves #32)

server/utils/downloadClients.js

@@ -156,6 +156,11 @@ class DownloadClientRegistry {
         result[type] = [];
       }
 
+      // Reset fallback flags for qBittorrent clients
+      if (client.resetFallbackFlag) {
+        client.resetFallbackFlag();
+      }
+
       try {
         const downloads = await client.getActiveDownloads();
         result[type].push(...downloads);