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/clients/jellyfin.py

@@ -12,6 +12,8 @@ from typing import Any, cast
 
 import requests
 
+from media_library_viewer_api.clients.http_timeout import DEFAULT_READ_TIMEOUT, http_timeout
+
 logger = logging.getLogger(__name__)
 
 
@@ -35,7 +37,7 @@ DEFAULT_FIELDS = ",".join(
 class JellyfinClient:
     """Small wrapper around the Jellyfin/Emby-compatible HTTP API."""
 
-    def __init__(self, base_url: str, api_key: str, timeout: int = 30):
+    def __init__(self, base_url: str, api_key: str, timeout: float = DEFAULT_READ_TIMEOUT):
         if not base_url:
             raise ValueError("Jellyfin URL is required")
         if not api_key:
@@ -47,7 +49,8 @@ class JellyfinClient:
         if self.base_url.endswith("/web"):
             self.base_url = self.base_url[:-4]
         self.api_key = api_key
-        self.timeout = timeout
+        # timeout is the per-response READ timeout (seconds); connect timeout is fixed at 5s.
+        self.timeout = http_timeout(timeout)
         self.session = requests.Session()
         self.session.headers.update(
             {