fix(security): close LOW ASVS findings — env bypass, SSE/deployment authz, CN fail-close, password byte-limit, exception leaks, BUG-12..16

Auth/session (V2.1.7, V4.1.5, V4.1.6, V2.1.4/V2.1.5):
- env secret validation no longer bypassed by attacker-injectable PYTEST* env;
  gated on explicit DECNET_TESTING=1 (set only in conftest).
- must_change_password now enforced on the SSE header-JWT path, not just ticket mint.
- GET /system/deployment-mode requires viewer auth (was leaking role + topology size).
- CreateUser/ResetUser passwords min_length=12; passwords >72 bytes rejected
  explicitly instead of bcrypt silently truncating.

Swarm ingestion (V9.1.3, BUG-16):
- Log listener hard-rejects peers with unparseable/empty cert CN (fail closed,
  ingests nothing) instead of tagging 'unknown'.
- Shutdown handlers no longer swallow real errors (narrowed to CancelledError).

Info leakage (V7.1.2, V14.1.2):
- Exception text sanitized on swarm-update, health, tarpit, realism, file-drop,
  blank-topology endpoints (raw tc/docker stderr, DB/Docker errors logged
  server-side, generic detail returned). pyproject license corrected to AGPL-3.0.

Correctness (BUG-12..16):
- BUG-12 atomic credential upsert (UNIQUE constraint + IntegrityError retry,
  consistent principal_key canonicalization).
- BUG-13 rule-tail watermark uses >= with seen-id dedup (no same-second drop).
- BUG-14 worker wake cleared before wait (no lost wake during tick).
- BUG-15 intel gather tolerates an unexpected provider raise.
- BUG-16 see above.

Already-closed (verified, no change): V2.1.6, V5.1.3, V9.1.2. Accept-risk +
documented: V2.1.8 cache window, V3.1.3 idle timeout. Tests added for every fix;
unanimous adversarial review after two refute-fix rounds.

decnet/intel/worker.py

@@ -108,10 +108,19 @@ async def _enrich_one(
         async with p._semaphore:
             return await p.lookup(ip)
 
-    results: list[IntelResult] = await asyncio.gather(
+    raw = await asyncio.gather(
         *(_guarded_lookup(p, ip) for p in providers),
-        return_exceptions=False,  # providers contractually never raise
+        return_exceptions=True,
     )
+    results: list[IntelResult] = []
+    for r in raw:
+        if isinstance(r, BaseException):
+            log.warning(
+                "intel: provider raised unexpectedly for ip=%s: %s",
+                ip, r,
+            )
+        else:
+            results.append(r)
 
     now = datetime.now(timezone.utc)
     row: dict[str, Any] = {
@@ -220,13 +229,13 @@ async def run_intel_loop(
                             attacker_uuid, ip,
                         )
 
+            wake.clear()
             try:
                 await asyncio.wait_for(
                     wake.wait(), timeout=float(poll_interval_secs),
                 )
             except asyncio.TimeoutError:
                 pass
-            wake.clear()
     except (asyncio.CancelledError, KeyboardInterrupt):
         log.info("intel worker stopped")
     finally: