fix(deps): bump pytest 7.4 → 8.4, pytest-cov 4.1 → 5.0 to satisfy pytest-asyncio 0.24

pytest-asyncio==0.24.0 (added on the FlowPilot branch as part of the
RLS test infra refactor) declares pytest>=8.2 — but requirements-dev.txt
still pinned pytest==7.4.3, so a clean pip install fails with
ResolutionImpossible. CI runners that started from a fresh image would
have refused to install dev deps; the FlowPilot tests passed locally
only because the dev container had a pre-installed pytest 8.x lying
around.

pytest-cov 4.1.0 also needs >= 5.0 to play nicely with pytest 8.

No code changes — pytest 8 is API-compatible with the existing test
suite once the install resolves.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/requirements-dev.txt

@@ -1,11 +1,11 @@
 # Include production dependencies
 -r requirements.txt
 
-# Testing
-pytest==7.4.3
+# Testing — pytest-asyncio 0.24+ requires pytest>=8.2
+pytest==8.4.2
 pytest-asyncio==0.24.0
 httpx>=0.27.0
-pytest-cov==4.1.0
+pytest-cov==5.0.0
 
 # Code quality
 black==24.1.1