fix: split HTTP connect/read timeouts (Jellyfin build + qBit stats)

Every HTTP client passed an integer timeout to requests, applying the same
value to BOTH connect and read phases. A slow Jellyfin /Items page or qBit
/sync/maindata blew through the 10s read budget → ReadTimeoutError. Split
into a (connect=5s, read=60s default) tuple via shared http_timeout() helper.
The media index build worker uses a 180s read floor. Existing services with
low timeout_seconds benefit from bumping to 60+.

backend/src/media_library_viewer_api/widgets/sources.py

@@ -115,7 +115,7 @@ class MetricSource:
             grafana_url = str(service.config.get("grafana_url") or "").rstrip("/")
             api_key = str(service.secrets.get("grafana_api_key") or "")
             datasource_uid = str(service.config.get("datasource_uid") or "prometheus")
-            timeout = int(service.config.get("timeout_seconds") or 10)
+            timeout = int(service.config.get("timeout_seconds") or 60)
             if widget_kind == "chart":
                 return await self._fetch_chart(grafana_url, api_key, datasource_uid, timeout, config)
             if widget_kind == "gauge":
@@ -277,7 +277,7 @@ class AlertmanagerWidgetSource:
             if service is None:
                 return {"error": "Alertmanager widget is missing its service"}
             base_url = str(service.config.get("base_url") or "").rstrip("/")
-            timeout = int(service.config.get("timeout_seconds") or 5)
+            timeout = int(service.config.get("timeout_seconds") or 60)
             severity_filter = config.get("severity_filter") or None
             headers: dict[str, str] = {}
             api_key = str(service.secrets.get("api_key") or "")
@@ -316,7 +316,7 @@ class JellyfinWidgetSource:
                 return {"error": "Jellyfin widget is missing its service"}
             base_url = str(service.config.get("base_url") or "")
             api_key = str(service.secrets.get("api_key") or "")
-            timeout = int(service.config.get("timeout_seconds") or 10)
+            timeout = int(service.config.get("timeout_seconds") or 60)
             client = await asyncio.wait_for(
                 asyncio.to_thread(JellyfinClient, base_url, api_key, timeout),
                 timeout=timeout,
@@ -396,7 +396,7 @@ class QbittorrentWidgetSource:
             base_url = str(service.config.get("base_url") or "")
             username = str(service.secrets.get("username") or "")
             password = str(service.secrets.get("password") or "")
-            timeout = int(service.config.get("timeout_seconds") or 10)
+            timeout = int(service.config.get("timeout_seconds") or 60)
             if not base_url or not username or not password:
                 return {"error": "qBittorrent service is missing base_url, username, or password"}