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_swarm.py

@@ -17,6 +17,8 @@ os.environ.setdefault("DECNET_JWT_SECRET", "schemathesis-swarm-secret-32chars-mi
 
 import pytest
 import schemathesis as st
+
+_QUICK = os.getenv("SCHEMA_QUICK") == "1"
 from schemathesis.checks import not_a_server_error
 from schemathesis.specs.openapi.checks import (
     status_code_conformance,
@@ -54,7 +56,7 @@ CHECKS = (
 @pytest.mark.fuzz
 @SCHEMA.parametrize()
 @settings(
-    max_examples=200,
+    max_examples=100 if _QUICK else 200,
     deadline=None,
     suppress_health_check=[
         HealthCheck.filter_too_much,