docs(images): publish the four screenshots from a clean window

[Gerrrt]

What changed

The four dashboard screenshots go into docs/images/, and the root README.md's
commented screenshot block becomes a live ## Dashboards section. No change to
the running lab — this is documentation only.

network-snmp.png and ups-power.png are replaced rather than left at their
#115 versions, so all four now come from one capture run.

Why

Closes #12. The last two boxes on that issue were "capture dashboard
screenshots" and "add them to the README", and the blocker was never the tooling
— it was the window. make screenshots shoots now-24h, and #62 fixed three
collection faults on the afternoon of 2026-08-21, so every image taken that day
pictured its own outage: a 14-hour hole across the host dashboard, 22 of 24
hours empty on the Docker one.

A one-shot timer re-ran the capture at 2026-08-22 16:30, past the point where
a full clean day sat behind it.

Blast radius

• No change to network segmentation or firewall rules
• No new port published to a VLAN that could not already reach the service
• No credential added outside secrets/*.sops.yaml

Documentation and one Makefile comment. Nothing deployed changes.

Verification

make validate — all checks pass, one skip (gitleaks not installed locally;
CI runs it).

Every image was read and checked against the pre-publish checklist in
docs/images/README.md:

Check	Result
Full 24-hour window, no gaps	all four
Full MAC addresses	none
WAN IP address	none — RFC1918 only (10.0.30.10, 10.7.7.2, 10.0.99.10)
Hostnames / usernames in tables or legends	device names only (prometheus, shiva, mjolnir, neo), all already published in docs/hardware.md
Container inventory panel	three allowlisted fields only — the compose.yaml path leak fixed in d1965f1 stays fixed

Two things visible in the images are real and deliberately kept rather than
re-shot around:

• network-snmp.png shows IloBatteryCondition firing on shiva. That is a
  genuine hardware fault tracked in IloBatteryCondition has been firing on shiva with no silence and no owner #76, and a picture of a stack with nothing
  wrong would be the less honest one.

• docker-containers.png carries a renderer series in two legends. That is
  the capture profile container taking the screenshot, which is why the
  inventory below it lists six containers and not seven.

• make validate passes

• Deployed to the lab and confirmed working — the images are the lab

• Docs updated (docs/images/README.md rewritten; the "why these two are
  absent" table is gone, the window warning and the Logs-dashboard exclusion
  stay)

Also fixes a one-word drift: Makefile:260 still said the capture shoots five
PNGs, which stopped being true when #108 dropped the Logs dashboard.

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