fix: prevent .card from collapsing in height-constrained flex columns

[howwohmm]

Fixes #147

Problem

.card sets overflow: hidden, which per CSS spec causes min-height: auto to resolve to 0 for flex items. When a .card is a direct child of a height-constrained flex column (e.g. main.vstack inside [data-sidebar-layout]), flex-shrink: 1 compresses the card to zero height.

Fix

.card {
  /* existing styles... */
  min-height: min-content;
}

One line. Ensures the card never shrinks below its content size while preserving overflow: hidden for border-radius clipping.

What it doesn't change

• overflow: hidden stays — still needed for content containment and border-radius
• Cards outside flex contexts are completely unaffected
• No size increase to speak of (1 declaration)

[knadh]

Missed this PR. Also, removing overflow: hidden entirely was the better approach. Fixed here: 072d84f