Show full weekday in dashboard date and time pill

[mot-yelraf]

Summary

Prepend the full weekday name to the dashboard date/time pill, separated by a space: Tuesday 2026-09-08 …. Preserve the existing date/time formatting and browser-local timezone. Update the app version to v0.26.251.8.

Verification

• npm run validate:pr: all 9 Playwright Chromium tests passed on macOS with Python 3.13.9.
• git diff --check: passed.
• A focused Chromium check before the punctuation adjustment verified full weekday rendering and fit at a 375px viewport.
• Used the isolated fixture host; no MQTT broker or direct hardware was involved.

Contributor checklist

• This pull request is focused on one logical change.
• Existing browser checks cover the dashboard; no new test file needed for this display formatting change.
• No canonical documentation update needed for this minor display change.
• I did not commit credentials, private runtime configuration, databases, or logs.
• Compatibility-sensitive MQTT, settings, switch identity, and persistence behavior is preserved.

Maintainer verification

• Remote checks pass: Python compile (3.11 and 3.13) and regression tests with coverage floor.
• npm run validate:pr passes on a trusted host.
• Unverified areas are recorded below.

Residual risk or unverified areas

Hardware, MQTT, and onboarding were not exercised; this change only affects the displayed date/time text.