fix(security): close MEDIUM ASVS findings — JWT pinning, SSE tickets, SSRF, mTLS pin, rate limits + correctness bugs

Auth (V2.1.1/V3.1.2, V2.1.3, V3.1.1):
- Pin JWT iss/aud/typ at mint and require+verify them at decode; revocation
  (jti denylist + tokens_valid_from) still enforced.
- Change-password now requires min_length=12.
- SSE auth moves off JWT-in-URL to a single-use 60s opaque ticket
  (POST /auth/sse-ticket); raw JWT in query no longer authenticates a stream.
  Removed dead fail-open get_stream_user helper.

Egress (V5.1.1, V9.1.1/V14.1.3):
- Webhook delivery + CRUD reject SSRF destinations (private/loopback/link-local/
  metadata, IPv4-mapped, multi-A-record) via resolved-IP validation, pin to the
  vetted IP, and never auto-follow redirects. Opt-out via DECNET_WEBHOOK_ALLOW_PRIVATE.
- UpdaterClient pins the worker leaf cert SHA-256 against the stored per-host
  fingerprint (fail closed on missing/mismatch); DECNET_VERIFY_HOSTNAME now
  defaults True.

Hardening (V13.1.3, V4.1.4, V13.1.2):
- Rate-limit change-password (5/min), enroll-bundle (10/min), webhook-create
  (20/min), host-delete (20/min) via the existing slowapi limiter.
- Correct false 'global auth middleware' comment; document enroll-bundle proxy
  trust.

Correctness (BUG-7..11):
- BUG-7 unbound bus in finally; BUG-8 apply_ceiling clamps to min(base,ceiling);
  BUG-9 commit before emit; BUG-10 multi-actor rearm for sub-threshold identities;
  BUG-11 normalize naive timestamps to UTC.

Already-closed (no change): V14.1.1, V2.1.2/V3.1.3, V5.1.2. Tests added for
every fix; unanimous adversarial review.

tests/api/auth/test_change_pass.py

@@ -4,6 +4,7 @@ import pytest
 from hypothesis import given, strategies as st, settings
 import httpx
 from decnet.env import DECNET_ADMIN_USER, DECNET_ADMIN_PASSWORD
+from decnet.web.limiter import limiter as _limiter
 from ..conftest import _FUZZ_SETTINGS
 
 @pytest.mark.anyio
@@ -57,6 +58,46 @@ async def test_fuzz_change_password(client: httpx.AsyncClient, old_password: str
             json=_payload,
             headers={"Authorization": f"Bearer {_token}"}
         )
-        assert _response.status_code in (200, 401, 422)
+        # 400: schema-guard middleware rejects bad length/shape (e.g. a
+        # new_password below the 12-char floor) before the handler runs.
+        assert _response.status_code in (200, 400, 401, 422)
     except (UnicodeEncodeError, json.JSONDecodeError):
         pass
+
+
+# ─── Rate-limit enforcement ─────────────────────────────────────────────────
+
+
+@pytest.mark.anyio
+async def test_change_password_rate_limit_trips_after_5(client: httpx.AsyncClient) -> None:
+    """5 change-password attempts from one IP → 6th returns 429."""
+    login_resp = await client.post(
+        "/api/v1/auth/login",
+        json={"username": DECNET_ADMIN_USER, "password": DECNET_ADMIN_PASSWORD},
+    )
+    token = login_resp.json()["access_token"]
+
+    for i in range(5):
+        r = await client.post(
+            "/api/v1/auth/change-password",
+            json={"old_password": f"wrong-{i}", "new_password": "does-not-matter-x!"},
+            headers={"Authorization": f"Bearer {token}"},
+        )
+        # 401 (bad old password) or 429 if the limiter fires — either is fine
+        assert r.status_code in (401, 429), f"attempt {i}: got {r.status_code}"
+
+    # The 6th attempt must trip the rate limiter (limit is 5/minute).
+    r = await client.post(
+        "/api/v1/auth/change-password",
+        json={"old_password": "still-wrong", "new_password": "does-not-matter-x!"},
+        headers={"Authorization": f"Bearer {token}"},
+    )
+    assert r.status_code == 429
+
+
+@pytest.mark.anyio
+async def test_change_password_route_has_rate_limit_decorator() -> None:
+    """Contract test: change_password handler must be wrapped by slowapi."""
+    from decnet.web.router.auth import api_change_pass as _mod
+
+    assert getattr(_mod.change_password, "__wrapped__", None) is not None