Add New Year visual theme

[C-ode-R]

Motivation

• Introduce a New Year / celebratory visual theme for the board UI across the Home view and global overlay.
• Add a prominent celebratory badge and color accents to make the interface feel festive without changing behavior.
• Refresh chip, lane, and panel colors to a night/celebration palette that pairs with confetti-style highlights.

Description

• Update src/views/HomeView.vue to add a .new-year-badge, adjust :root CSS variables, and apply new palette and decorative ::before/::after topbar accents.
• Replace the holiday tree icon with a sparkle and recolor cards, pills, lanes, chips, and the D‑Day panel to match the New Year theme.
• Update src/App.vue .snow-overlay to include colored radial gradients, additional sparkle animation (@keyframes sparkle), adjusted opacity, and revised background sizes/positions to simulate festive confetti/sparkles.
• All changes are visual/CSS only and do not alter application logic or runtime behavior.

Testing

• Ran npm run dev which started Vite and served the app successfully (local and network URLs reported).
• Attempted an automated Playwright screenshot to validate visuals, but the Chromium process crashed with a SIGSEGV in this environment so no screenshot was captured.
• No unit or integration test suites were executed for these visual-only changes.

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Codex Task