docs: refresh screenshots and images to current dashboard/branding

[VijitSingh97]

The images embedded in the README and docs have drifted from the current dashboard UI and branding, and should be recaptured.

Images to update

Referenced in README.md:

• images/pithead-mark.svg — header mark
• images/launch/hero.png / hero-light.png — hero shot
• images/launch/demo.gif — dashboard tour

Referenced in docs/dashboard.md:

• images/launch/sync.png / sync-light.png — Sync Mode
• images/launch/simple.png / simple-light.png — Simple view
• images/launch/advanced.png / advanced-light.png — Advanced view

Also present but not currently linked from docs (check for staleness): images/dashboard.png, images/syncing.png, images/launch/social-preview.png.

Why

• Last captured for the Launch assets: refreshed hero screenshot + demo GIF + GitHub social preview #80 launch assets (commit 8f3005e); the dashboard has changed since (Sync Mode, Simple/Advanced views, Telegram/onion additions).
• Logo/wordmark assets may still reflect pre-Pithead branding.

Done when

• Each light/dark pair is recaptured from the current dashboard at a consistent viewport.
• README and docs/dashboard.md render correctly in both color schemes.
• Any unused legacy images removed or re-linked.

[VijitSingh97]

Status (2026-07-12): release-time live capture — not a code change.

The four other v1.5 late-additions (#493/#489/#470/#477) are merged to develop-v1.5; this one is held because its "Done when" requires recapturing each light/dark pair from the current running dashboard at a consistent viewport. Doing that authentically needs a live stack with real fleet/history data — the existing shots (advanced, simple, hero, sync, demo.gif) show a real deployment, and replacing them with fixture-driven synthetic renders (empty charts, placeholder workers) would be a regression, not a refresh.

Best captured on the bench (gouda) or prod dashboard right before the v1.5 cut, when the new Worker Inspect page (#185) and Energy tab (#260) are live with data. The logo/wordmark half is separately blocked on a new Pithead mark being designed (the PNGs still carry the pre-rename wordmark).

Recommended: keep in v1.5, do it as a release-runbook step alongside the cut. No blocker on the feature work.

[VijitSingh97]

Moved to v1.7 and sequenced LAST in the cycle (see #531): #518/#529/#502 change every screen this would capture — recapture once the config-UX work settles.