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/tests/test_http_timeout.py

@@ -0,0 +1,39 @@
+"""Tests for the shared HTTP timeout helper."""
+
+from __future__ import annotations
+
+from media_library_viewer_api.clients.http_timeout import (
+    DEFAULT_CONNECT_TIMEOUT,
+    DEFAULT_READ_TIMEOUT,
+    http_timeout,
+)
+
+
+class TestHttpTimeout:
+    def test_http_timeout_returns_tuple(self) -> None:
+        result = http_timeout(30)
+        assert result == (DEFAULT_CONNECT_TIMEOUT, 30.0)
+
+    def test_http_timeout_default_when_none(self) -> None:
+        result = http_timeout(None)
+        assert result == (DEFAULT_CONNECT_TIMEOUT, DEFAULT_READ_TIMEOUT)
+
+    def test_http_timeout_default_when_zero(self) -> None:
+        result = http_timeout(0)
+        assert result == (DEFAULT_CONNECT_TIMEOUT, DEFAULT_READ_TIMEOUT)
+
+    def test_http_timeout_custom_connect(self) -> None:
+        result = http_timeout(30, connect_timeout=10)
+        assert result == (10.0, 30.0)
+
+    def test_http_timeout_default_when_negative(self) -> None:
+        result = http_timeout(-5)
+        assert result == (DEFAULT_CONNECT_TIMEOUT, DEFAULT_READ_TIMEOUT)
+
+    def test_http_timeout_default_when_garbage_string(self) -> None:
+        result = http_timeout("garbage")  # type: ignore[arg-type]
+        assert result == (DEFAULT_CONNECT_TIMEOUT, DEFAULT_READ_TIMEOUT)
+
+    def test_http_timeout_accepts_int(self) -> None:
+        result = http_timeout(45)
+        assert result == (5.0, 45.0)