Roadmap: kernel timestamps and service hardening

[EONRaider]

Roadmap epic: move the raw-socket capture path from a single-interface, userspace-timestamped, Ctrl-C-only loop toward service-grade capture. Split into independent sub-issues, ordered by dependency:

• Kernel timestamps via SO_TIMESTAMPNS #59 — Kernel timestamps via SO_TIMESTAMPNS (Small–Medium)
• Graceful shutdown on SIGTERM #60 — Graceful shutdown on SIGTERM (Small)
• Concurrent multi-interface capture #61 — Concurrent multi-interface capture (Medium–Large; best after Kernel timestamps via SO_TIMESTAMPNS #59/Graceful shutdown on SIGTERM #60)

#59 and #60 are self-contained quick wins. #61 is a design change to capture() and couples to #59 (kernel timestamps make cross-interface ordering meaningful). All three follow the socketless test seam established in #57 — the privileged PF_PACKET behavior stays behind a gated integration test.

[EONRaider]

Both sub-issues shipped: #59 (kernel timestamps, nanosecond precision end-to-end) in #67, #61 (concurrent multi-interface capture, asyncio-based) in #69.