spec: add SPEC-003 full machine inventory in connection DB

Persist a complete per-machine device inventory on connect_machines
(OS+locale+install, CPU/RAM, mfr/model/serial, external WAN IP captured
server-side via trusted-proxy client_ip + private LAN IP + MAC, logged-on
user, idle, time zone, uptime, local-admin-present), refreshed each
AgentStatus and surfaced in the dashboard machine detail — ScreenConnect
"Guest Info" parity. Data layer for SPEC-002 Phase 2; closes the GC side
of the agent-IP gap (coord todo 7459428e). Requested by Mike 2026-05-30.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/FEATURE_ROADMAP.md

@@ -47,6 +47,7 @@ Bringing GC to parity with GuruRMM's release engineering. Full plan: [SPEC-001](
 
 - [x] JWT auth, Argon2id passwords, rate limiting, security headers
 - [x] Sessions / machines / support-codes / events
+- [ ] **Full machine inventory in the connection DB** — P2 — persist per-machine device inventory (OS+locale+install, CPU/RAM, mfr/model/serial, external WAN IP captured server-side + private LAN IP + MAC, logged-on user, idle, time zone, uptime, local-admin) on `connect_machines`, refreshed each `AgentStatus`, shown in the dashboard machine detail (ScreenConnect "Guest Info" parity). Data layer for SPEC-002 Phase 2; closes GC side of agent-IP gap (todo 7459428e). ([SPEC-003](specs/SPEC-003-machine-inventory.md))
 - [ ] Programmatic session pre-create + viewer-token (integration contract) — P2
 
 ## Security & Infrastructure