added: profiling toolchain (py-spy, pyinstrument, pytest-benchmark, memray, snakeviz)

New `profile` optional-deps group, opt-in Pyinstrument ASGI middleware
gated by DECNET_PROFILE_REQUESTS, bench marker + tests/perf/ micro-benchmarks
for repository hot paths, and scripts/profile/ helpers for py-spy/cProfile/memray.

tests/perf/conftest.py

@@ -0,0 +1,36 @@
+import asyncio
+import pytest
+
+from decnet.web.db.factory import get_repository
+
+
+@pytest.fixture(scope="session")
+def event_loop():
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.close()
+
+
+@pytest.fixture(scope="session")
+def repo(tmp_path_factory, event_loop):
+    path = tmp_path_factory.mktemp("perf") / "bench.db"
+    r = get_repository(db_path=str(path))
+    event_loop.run_until_complete(r.initialize())
+    return r
+
+
+@pytest.fixture(scope="session")
+def seeded_repo(repo, event_loop):
+    async def _seed():
+        for i in range(1000):
+            await repo.add_log({
+                "decky": f"decky-{i % 10:02d}",
+                "service": ["ssh", "ftp", "smb", "rdp"][i % 4],
+                "event_type": "connect",
+                "attacker_ip": f"10.0.{i // 256}.{i % 256}",
+                "raw_line": f"event {i}",
+                "fields": "{}",
+                "msg": "",
+            })
+    event_loop.run_until_complete(_seed())
+    return repo