feat(activesync): optional last_command / in_flight request touches

[TDannhauer]

Parent

Epic: horde/ActiveSync#99
Follow-up (after v1 ops monitor is in use)
Design: horde/ActiveSync doc/ops-monitor.md (§9.1, Issue G)

Summary

Optional, config-gated request lifecycle fields so “active / stuck mid-Sync” is real rather than inferred:

• e.g. last_command, last_http_status, last_eas_status, in_flight_since
• Written at request start/end in Core RPC / ActiveSync driver path
• Privacy-safe only (no subjects / bodies / addresses)

May also touch horde/rpc.

Acceptance

• Off by default
• Snapshot/CLI/Web can surface in-flight requests
• No PII beyond existing admin device identity fields
• Document conf key in ActiveSync/Horde configuration docs

Depends

Ship after the v1 CLI (hordectl activesync top) has production feedback on missing signals.

[TDannhauer]

Depends on v1 CLI feedback from horde-activesync top (horde/base#146), not hordectl.