Dashboard: flat single-layer design pass + honest all-time trends

[e35ventura]

What changed

Design pass: one card layer on a black canvas

• Removed the outer wrapper cards around every dashboard section (Active Network, Contribution Calendar, OSS Contributions, Issue Discoveries, Featured Contributors/Discoverers/Work, Live Activity). Section labels now sit directly on the canvas with exactly one card layer beneath them.
• All controls speak one language: no pill fills, outlines, or sliders — only the selected item's text takes color. Applied to the chart mode toggle, the 1D/7D/35D/ALL range selector, and the calendar month selector.
• Chart legend chips are now plain series-colored words matching the lines on the chart; click-to-toggle and shift-to-solo behavior preserved.
• Status badges (OPENED/MERGED/CLOSED) and Eligible/Ineligible badges are plain colored words instead of chips.
• Live Activity: gray card fills and status gradient washes removed, filter row and pulse dot removed (feed always shows all activity), open PRs read OPENED, and the header/card edges align pixel-exact with the Active Network column top and bottom.

Fix: all-time trend chart

• The all-time view's weekly buckets were calendar-aligned, so the last bucket was the partial current week and every series nosedived at the right edge. Buckets are now anchored to the current time, so the last point always covers a full trailing 7 days (verified against live API counts).
• All-time labels carry the full week range and year in the tooltip ("Dec 14 – 20, 2025") while the axis shows the compact start date, resolving the year ambiguity across the Dec–Jan boundary.

Before / After

Dashboard (35D default)

Before	After

All-time range (note the fake right-edge cliff in Before)

Before	After

Validation

• npm run build passes; lint-staged ran on commit.
• Screenshot-verified at desktop width: alignment, wrapping, and the all-time chart's right edge match the underlying data.