fix(stats-export): full-resolution preview, fit Square in modal (#740)

* fix(stats-export): full-resolution preview, fit Square in modal

Reported on the Psysonic Discord — three connected issues with the
**Share Top Albums** dialog on the Statistics page:

1. **Square preview clipped.** `PreviewFrame` capped only `maxHeight: 52vh`
   while letting `width: 100%` + `aspectRatio: 1/1` push the 1:1 canvas
   far past the cap; `overflow: hidden` then chopped the bottom rows
   with no way to scroll them in (Twitter is width-bound, Story is
   width-capped at 320px, so Square was the only ratio that overflowed).
   Cap **both** dimensions per format — Square gets `maxWidth: 52vh`,
   Story gets `min(320px, calc(52vh * 9/16))`, Twitter stays
   width-bound by the modal — so the preview always fits.

2. **Outer scrolling didn't reveal the bottom.** Same root cause: the
   modal-content scroll only exposed the action buttons; the canvas
   itself sat inside `overflow: hidden` with nothing more to scroll to.
   Fixed implicitly by (1).

3. **Preview is blurry.** `PREVIEW_MAX_WIDTH = 540` rendered a 540×540
   canvas that CSS then stretched back to ~676px in a 720px-wide modal,
   and `desiredTilePx = 256` decoded covers at 256 px only to upscale
   them into ~300 px tiles. Render the preview canvas at the full
   export width (1080) and decode covers at the export tile size (600)
   so text is sharp and covers downsample crisply.

* docs(changelog): stats-export preview fix (PR #740)

src/components/StatsExportModal.tsx

@@ -282,22 +282,24 @@ export default function StatsExportModal({ open, albums, meta, onClose }: Props)
 }
 
 const PreviewFrame = ({ format, children }: { format: ExportFormat; children: React.ReactNode }) => {
-  const aspect = useMemo(() => {
-    if (format === 'story')   return '9 / 16';
-    if (format === 'square')  return '1 / 1';
-    return '16 / 9';
+  // Aspect-aware bounds: cap BOTH dimensions so the preview always fits inside
+  // the modal at any ratio. The earlier version capped only `maxHeight`, so
+  // Square (1:1) tried to span the full modal width — the 1:1 canvas then
+  // overflowed `maxHeight: 52vh` and the bottom rows were clipped by
+  // `overflow: hidden` with no way to scroll them into view.
+  const { aspect, maxWidth } = useMemo(() => {
+    if (format === 'story')   return { aspect: '9 / 16', maxWidth: 'min(320px, calc(52vh * 9 / 16))' };
+    if (format === 'square')  return { aspect: '1 / 1',  maxWidth: '52vh' };
+    return                          { aspect: '16 / 9', maxWidth: undefined as string | undefined };
   }, [format]);
-  // Cap preview height so the modal stays manageable on a typical desktop.
-  // Narrow ratios (Story) become height-bounded; wide ratios (Twitter) are
-  // width-bounded by the modal itself.
   return (
     <div style={{
       position: 'relative',
       width: '100%',
-      maxHeight: '52vh',
       aspectRatio: aspect,
       margin: '0 auto',
-      maxWidth: format === 'story' ? '320px' : undefined,
+      maxWidth,
+      maxHeight: '52vh',
       background: 'var(--glass-bg)',
       borderRadius: 12,
       border: '1px solid var(--glass-border)',

src/utils/export/exportAlbumCard.ts

@@ -32,7 +32,11 @@ const DIMENSIONS: Record<ExportFormat, { w: number; h: number }> = {
   twitter: { w: 1200, h: 675 },
 };
 
-const PREVIEW_MAX_WIDTH = 540;
+// Preview canvas resolution. 540 left text and album covers visibly upscaled
+// (and so blurry) when CSS stretched the canvas back up to the modal width
+// — match the full export width for Square/Story (1080) so the preview is
+// pixel-crisp at any modal size, and only Twitter scales down (1200 → 1080).
+const PREVIEW_MAX_WIDTH = 1080;
 
 /** Reads a `--var` from `document.documentElement`, with optional fallback. */
 function readThemeVar(name: string, fallback: string): string {
@@ -252,7 +256,10 @@ export async function renderAlbumCardCanvas(opts: ExportAlbumCardOptions): Promi
   }
 
   // ── Tiles ────────────────────────────────────────────────────────────────
-  const desiredTilePx = preview ? 256 : 600;
+  // Match the export tile resolution so preview covers downsample crisply
+  // into the (now full-width) canvas instead of upscaling 256 → ~300 and
+  // blurring every album thumbnail.
+  const desiredTilePx = 600;
   const needed = gridSize * gridSize;
   const tilesAlbums = albums.slice(0, needed);
   const covers = await Promise.all(tilesAlbums.map(a => loadAlbumCover(a, desiredTilePx)));