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/router/swarm/api_decommission_host.py

@@ -12,12 +12,13 @@ from __future__ import annotations
 
 import pathlib
 
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, Request, status
 
 from decnet.logging import get_logger
 from decnet.swarm.client import AgentClient
 from decnet.web.db.repository import BaseRepository
 from decnet.web.dependencies import get_repo, require_admin
+from decnet.web.limiter import limiter
 from decnet.web.router.swarm._mtls import PeerCert, require_operator_cert
 
 log = get_logger("swarm.decommission")
@@ -32,10 +33,13 @@ router = APIRouter()
         401: {"description": "Missing or invalid admin JWT"},
         403: {"description": "Authenticated user is not an admin, or operator cert missing"},
         404: {"description": "No host with this UUID is enrolled"},
+        429: {"description": "Too many decommission requests — retry after the window resets"},
     },
 )
+@limiter.limit("20/minute")
 async def api_decommission_host(
     uuid: str,
+    request: Request,
     repo: BaseRepository = Depends(get_repo),
     _admin: dict = Depends(require_admin),
     _operator: PeerCert = Depends(require_operator_cert),