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.

decnet/web/auth.py

@@ -11,6 +11,14 @@ SECRET_KEY: str = DECNET_JWT_SECRET
 ALGORITHM: str = "HS256"
 ACCESS_TOKEN_EXPIRE_MINUTES: int = DECNET_JWT_EXP_MINUTES
 
+# Pinned issuer/audience/type so a token signed with DECNET_JWT_SECRET for any
+# OTHER purpose (or by a future co-tenant of the secret) is not accepted by the
+# dashboard verifier. Issuance stamps these; _decode_payload requires + verifies
+# them. Keep these two modules in lockstep — they are a single trust contract.
+JWT_ISSUER: str = "decnet"
+JWT_AUDIENCE: str = "decnet-dashboard"
+JWT_TYPE: str = "access"
+
 
 def verify_password(plain_password: str, hashed_password: str) -> bool:
     return bcrypt.checkpw(
@@ -45,5 +53,10 @@ def create_access_token(data: dict[str, Any], expires_delta: Optional[timedelta]
 
     _to_encode.update({"exp": _expire})
     _to_encode.update({"iat": datetime.now(timezone.utc)})
+    # Pin issuer / audience / token-type so the verifier can reject tokens
+    # minted for any other purpose with the same shared secret.
+    _to_encode.setdefault("iss", JWT_ISSUER)
+    _to_encode.setdefault("aud", JWT_AUDIENCE)
+    _to_encode.setdefault("typ", JWT_TYPE)
     _encoded_jwt: str = jwt.encode(_to_encode, SECRET_KEY, algorithm=ALGORITHM)
     return _encoded_jwt