test(be): every dependency override goes through override_dep

22 test files set `app.dependency_overrides[...]` by hand and tore down with a blanket `.clear()`
in a `finally`, which wipes every override rather than the test's own and stops fixtures composing.
They now take the `override_dep` fixture (helpers get it passed in), whose teardown restores each
key's prior value; no clear() carried meaning between two phases of a test. A convention test fails
any test file that writes `dependency_overrides` directly.

backend/tests/test_saved_views_source.py

@@ -11,12 +11,12 @@ from app.main import app
 from app.models import User
 
 
-def _client(db, user, monkeypatch):
+def _client(db, user, monkeypatch, override_dep):
     monkeypatch.setattr(
         state, "_configured_cache", True
     )  # the request gate 503s an unconfigured app
-    app.dependency_overrides[get_db] = lambda: db
-    app.dependency_overrides[current_user] = lambda: user  # require_human resolves through this
+    override_dep(get_db, lambda: db)
+    override_dep(current_user, lambda: user)  # require_human resolves through this
     return TestClient(app)
 
 
@@ -27,56 +27,43 @@ def _user(db):
     return u
 
 
-def test_views_are_scoped_by_source(db, monkeypatch):
+def test_views_are_scoped_by_source(db, monkeypatch, override_dep):
     user = _user(db)
-    try:
-        c = _client(db, user, monkeypatch)
-        # Same NAME under two sources is allowed (unique is per user+source now).
-        f = c.post(
-            "/api/saved-views", json={"name": "Fresh", "filters": {"a": 1}, "source": "feed"}
-        )
-        p = c.post(
-            "/api/saved-views", json={"name": "Fresh", "filters": {"b": 2}, "source": "plex"}
-        )
-        assert f.status_code == 200 and p.status_code == 200, (f.text, p.text)
+    c = _client(db, user, monkeypatch, override_dep)
+    # Same NAME under two sources is allowed (unique is per user+source now).
+    f = c.post("/api/saved-views", json={"name": "Fresh", "filters": {"a": 1}, "source": "feed"})
+    p = c.post("/api/saved-views", json={"name": "Fresh", "filters": {"b": 2}, "source": "plex"})
+    assert f.status_code == 200 and p.status_code == 200, (f.text, p.text)
 
-        feed = c.get("/api/saved-views?source=feed").json()
-        plex = c.get("/api/saved-views?source=plex").json()
-        assert [v["name"] for v in feed] == ["Fresh"]
-        assert [v["name"] for v in plex] == ["Fresh"]
-        assert feed[0]["filters"] == {"a": 1} and plex[0]["filters"] == {"b": 2}
-        # A source-less GET keeps the old feed-only behaviour.
-        assert [v["id"] for v in c.get("/api/saved-views").json()] == [v["id"] for v in feed]
-    finally:
-        app.dependency_overrides.clear()
+    feed = c.get("/api/saved-views?source=feed").json()
+    plex = c.get("/api/saved-views?source=plex").json()
+    assert [v["name"] for v in feed] == ["Fresh"]
+    assert [v["name"] for v in plex] == ["Fresh"]
+    assert feed[0]["filters"] == {"a": 1} and plex[0]["filters"] == {"b": 2}
+    # A source-less GET keeps the old feed-only behaviour.
+    assert [v["id"] for v in c.get("/api/saved-views").json()] == [v["id"] for v in feed]
 
 
-def test_default_is_per_source(db, monkeypatch):
+def test_default_is_per_source(db, monkeypatch, override_dep):
     user = _user(db)
-    try:
-        c = _client(db, user, monkeypatch)
-        fid = c.post(
-            "/api/saved-views", json={"name": "F", "filters": {}, "source": "feed"}
-        ).json()["id"]
-        pid = c.post(
-            "/api/saved-views", json={"name": "P", "filters": {}, "source": "plex"}
-        ).json()["id"]
-        c.patch(f"/api/saved-views/{fid}", json={"is_default": True})
-        c.patch(f"/api/saved-views/{pid}", json={"is_default": True})
-        # Making the Plex view default must NOT clear the feed view's default (different source).
-        assert c.get("/api/saved-views?source=feed").json()[0]["is_default"] is True
-        assert c.get("/api/saved-views?source=plex").json()[0]["is_default"] is True
-    finally:
-        app.dependency_overrides.clear()
+    c = _client(db, user, monkeypatch, override_dep)
+    fid = c.post("/api/saved-views", json={"name": "F", "filters": {}, "source": "feed"}).json()[
+        "id"
+    ]
+    pid = c.post("/api/saved-views", json={"name": "P", "filters": {}, "source": "plex"}).json()[
+        "id"
+    ]
+    c.patch(f"/api/saved-views/{fid}", json={"is_default": True})
+    c.patch(f"/api/saved-views/{pid}", json={"is_default": True})
+    # Making the Plex view default must NOT clear the feed view's default (different source).
+    assert c.get("/api/saved-views?source=feed").json()[0]["is_default"] is True
+    assert c.get("/api/saved-views?source=plex").json()[0]["is_default"] is True
 
 
-def test_duplicate_name_within_a_source_conflicts(db, monkeypatch):
+def test_duplicate_name_within_a_source_conflicts(db, monkeypatch, override_dep):
     user = _user(db)
-    try:
-        c = _client(db, user, monkeypatch)
-        a = c.post("/api/saved-views", json={"name": "Dup", "filters": {}, "source": "plex"})
-        b = c.post("/api/saved-views", json={"name": "Dup", "filters": {}, "source": "plex"})
-        assert a.status_code == 200
-        assert b.status_code == 409  # same (user, source, name)
-    finally:
-        app.dependency_overrides.clear()
+    c = _client(db, user, monkeypatch, override_dep)
+    a = c.post("/api/saved-views", json={"name": "Dup", "filters": {}, "source": "plex"})
+    b = c.post("/api/saved-views", json={"name": "Dup", "filters": {}, "source": "plex"})
+    assert a.status_code == 200
+    assert b.status_code == 409  # same (user, source, name)