The aria-hidden glyph + sr-only label markup was hand-copied in LetterCard
and YearLetterStrip. Extract a small GlyphLabel component and use it at
both sites so the accessibility idiom has a single owner.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The dense-year strip count now carries the ✉ glyph (aria-hidden + sr-only
"Brief"), and beneath the sparkline a "Monats-Dichte" caption sits between
the two endpoint month labels (Jan/Dez {year}) at the ≥10px micro-axis
floor, localized via the shared month formatter. The ≥44px keyboard-
focusable "Briefe anzeigen" expand toggle is preserved unchanged.
Refs #833
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Letter count + 12-month density sparkline + a >=44px keyboard-focusable expand
toggle that reveals that year's LetterCards (REQ-012). Sparkline values from the
shared monthHistogram.
Refs #779
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
