musl libc has weak fork-safety guarantees in multi-threaded processes.
When Tokio's runtime is running and we fork() for SNMP operations, musl's
internal state can be inconsistent in the child, causing SIGSEGV on every
SNMP walk to Ubiquiti devices. glibc handles this via pthread_atfork.
- Dockerfile: Alpine → rust:1.93-bookworm build + debian:12-slim runtime
- CI: Remove ensure-netsnmp-base/manifest jobs, simplify build deps
- Delete Dockerfile.netsnmp and netsnmp-base.yml workflow
- Add NULL pointer guards in snmp_helper.c for fork-safety
- Add SNMP exception type handling (NoSuchObject/Instance/EndOfMibView)
- Add crash reproduction tests
Verifies that ring is properly installed as the default crypto provider
and that all TLS-dependent operations work: rustls ClientConfig, reqwest
client, tokio-rustls connector, and WebSocket TLS with webpki roots.
These tests catch the CryptoProvider panic before it reaches production.
