- decnet/env.py: DECNET_JWT_SECRET and DECNET_ADMIN_PASSWORD are now
required env vars; startup raises ValueError if unset or set to a
known-bad default ("admin", "password", etc.)
- decnet/env.py: add DECNET_CORS_ORIGINS (comma-separated, defaults to
http://localhost:8080) replacing the previous allow_origins=["*"]
- decnet/web/api.py: use DECNET_CORS_ORIGINS and tighten allow_methods
and allow_headers to explicit lists
- tests/conftest.py: set required env vars at module level so test
collection works without real credentials
- tests/test_web_api.py, test_web_api_fuzz.py: use DECNET_ADMIN_PASSWORD
from env instead of hardcoded "admin"
Closes DEBT-001, DEBT-002, DEBT-004
