feat(test): add test-schema target and SCHEMA_QUICK=1 mode for schemathesis

- Add dedicated test-schema Makefile target (xdist logical, 600s timeout,
  -m fuzz) so schemathesis runs separately from test-fuzz, which was
  spinning up competing uvicorn workers per xdist process
- Exclude all test_schemathesis*.py files from FUZZ_FLAGS via --ignore
- Add schema to _ALL_SUITES between api and fuzz
- Add SCHEMA_QUICK env var (default 0): caps every max_examples to 100
  across all four schemathesis files (4520 -> 600 total examples)
- Fix pre-push hook: use .311 venv and delegate to make test-all FAIL_FAST=0
  instead of hand-rolling five separate pytest invocations

tests/api/test_schemathesis.py

@@ -40,6 +40,7 @@ def _free_port() -> int:
 LIVE_PORT = _free_port()
 LIVE_SERVER_URL = f"http://127.0.0.1:{LIVE_PORT}"
 TEST_SECRET = "test-secret-for-automated-fuzzing"
+_QUICK = os.getenv("SCHEMA_QUICK") == "1"
 
 import decnet.web.auth
 decnet.web.auth.SECRET_KEY = TEST_SECRET
@@ -144,7 +145,7 @@ schema = st.openapi.from_url(f"{LIVE_SERVER_URL}/openapi.json")
 @pytest.mark.fuzz
 @st.pytest.parametrize(api=schema)
 @settings(
-    max_examples=3000,
+    max_examples=100 if _QUICK else 3000,
     deadline=None,
     verbosity=Verbosity.debug,
     suppress_health_check=[
@@ -161,7 +162,7 @@ def test_schema_compliance(case):
 @pytest.mark.fuzz
 @st.pytest.parametrize(api=schema)
 @settings(
-    max_examples=500,
+    max_examples=100 if _QUICK else 500,
     deadline=None,
     verbosity=Verbosity.normal,
     suppress_health_check=[