test: the gate's output carries no noise to hide a real warning in

- Home tests mocked the api without downloadIndex, so every card's download button logged a
  missing-queryFn error (64 stderr blocks per run).
- QueryState rendered without an i18n instance; Modal.fullscreen awaited a synchronous act,
  which React reports as an act environment it does not support.
- pytest: Starlette 1.x's TestClient is built on httpx2 and warned on every run without it
  (pinned in requirements-dev); alembic.ini declares its path separator.

backend/alembic.ini

@@ -1,6 +1,8 @@
 [alembic]
 script_location = alembic
 prepend_sys_path = .
+# Split the path list the way the OS does (alembic's legacy space/comma/colon split is deprecated).
+path_separator = os
 
 [loggers]
 keys = root,sqlalchemy,alembic

backend/requirements-dev.txt

@@ -1,7 +1,9 @@
 # Test + lint tooling — NEVER in the prod image. Installed only by backend/Dockerfile.test (the
 # throwaway test image), which the prod build (root Dockerfile) never references. Pinned so the
 # suite is reproducible: pytest for the pure-logic tests, and ruff at the SAME version the gate's
-# backend lint lane currently runs on the host (see the run_lint note in siftlode.sh). httpx is
-# already an app dependency (requirements.txt), so its TestClient needs nothing extra here.
+# backend lint lane runs on the host (the gate fails when the host's ruff is not this one). httpx2:
+# Starlette 1.x's TestClient is built on it (`import httpx2 as httpx`) and only falls back to the
+# app's own httpx with a deprecation warning on every run.
 pytest==8.4.2
 ruff==0.15.21
+httpx2==2.13.0