Spotify Widget

### Description

Goal
Add a Spotify widget to Glance so users can discover music and open it in Spotify without leaving their dashboard.

Key Features

New Releases & Featured Playlists (localized by country).

Clickable cards (artwork, title, artist, release date) that deep‑link to Spotify.

Responsive, visually consistent grid with hover animations and graceful error states.

Configurable item count, content type, country, and cache duration.

Config

Uses type: spotify with client-id/client-secret.

Advanced options: content-type (new-releases or featured-playlists), country, limit, cache.

APIs & Auth

OAuth2 Client Credentials (no user login/personal data).

Endpoints: /api/token, /browse/new-releases, /browse/featured-playlists, /browse/categories.

Mind rate limits and regional availability per Spotify docs.

Implementation

Matches existing Glance widget patterns (templates, caching, error handling).

Go HTTP client with timeouts; responsive CSS grid; theme support.

Security

Credentials via environment variables; read‑only public catalog access.

Risks/Tradeoffs

Requires Spotify developer creds; subject to rate limits, regional restrictions, and API changes; mainly benefits Spotify users.

Precedents

Similar integrations exist in Rainmeter, Übersicht, Home Assistant, Grafana, and many personal dashboards.

Extensibility

Pattern can extend to Apple Music/YouTube Music, podcasts, or (with extra auth) user‑personalized content.

Value
Completes Glance’s media coverage by adding music discovery while keeping the dashboard fast, lightweight, and optional for users who don’t need it.