docs: Phase 5 — incident log, maintenance runbook, NUT config archive

beast/nut/upssched.conf: fixed earlyshutdown timer (30s→300s) and added
  cancel rule. Archived post-fix from Beast.
beast/nut/upssched-cmd: archived for reference.

runbooks/phase5-incident-log.md:
  INC-005: NUT upssched earlyshutdown bug — cause, fix, break-test findings.
  INC-001 through INC-004: PBS USB hub/data/re-diagnosis/sdj end-of-life.
  P5-01 through P5-11: pending work queue including Pi4 node-exporter,
  compute5 PCIe PM, PBS recovery gate, qnetd migration, Authelia metrics,
  cert renewal verification, ansible-control disk, Phase 4A resume.

runbooks/maintenance-runbook.md: PBS recovery steps, UPS test procedure,
  cert renewal schedule (May 11/18), Phase 4A per-node procedure, qnetd
  migration, Authelia metrics setup, recurring checklist.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

beast/nut/upssched.conf

@@ -0,0 +1,14 @@
+CMDSCRIPT /etc/nut/upssched-cmd
+PIPEFN /etc/nut/upssched.pipe
+LOCKFN /etc/nut/upssched.lock
+
+AT ONBATT * START-TIMER onbatt 30
+AT ONLINE * CANCEL-TIMER onbatt online
+AT ONBATT * START-TIMER earlyshutdown 300
+AT ONLINE * CANCEL-TIMER earlyshutdown online
+AT LOWBATT * EXECUTE onbatt
+AT COMMBAD * START-TIMER commbad 30
+AT COMMOK * CANCEL-TIMER commbad commok
+AT NOCOMM * EXECUTE commbad
+AT SHUTDOWN * EXECUTE powerdown
+AT SHUTDOWN * EXECUTE powerdown