Adds a Style picker (Plain / Accent / Colorful) to the Customize Home
sheet, shown when the shortcuts layout is Cards. Defaults to Plain.
- Plain: current look (light accent tint + accent border)
- Accent: solid accent fill, white icon/text
- Colorful: solid fill with a fixed color per shortcut type
The filled styles use a Reminders-style layout (icon top-leading, count
top-trailing, title anchored to the bottom) with a subtle gradient sheen
over the fill color. Cards without a meaningful count (Open Link, Remote,
Subscriptions, instance content, media sources) hide the number; Remote
shows its status dot in the top-right slot instead.
Persisted via SettingsKey.homeShortcutCardStyle, mirroring the existing
homeShortcutLayout accessor.
Color.accentColor and .foregroundStyle(.tint) resolve to the asset
catalog accent on macOS, so Home shortcut cards, section header
links, the Subscriptions "All channels" header, and the Downloads
per-channel group headers stayed blue when the user picked a
different accent. Read the color from SettingsManager and apply it
directly, matching the pattern already used for the Play button.
