- Atomic writes in store (write-to-temp + rename) to prevent
  corruption on crash
- Validate DHT results against requested content hash to reject
  forged data from malicious nodes
- Limit protocol line size to 128 KiB on Unix socket to prevent
  memory exhaustion
- Use saturating_add for TTL expiry to prevent u64 overflow

DHT-backed encrypted pastebin with two binaries (tp/tpd),
XChaCha20-Poly1305 encryption, content-addressed storage,
and Unix socket + HTTP interfaces.