fix(flutter): bump album-grid cellH slack — silence 1px overflow warnings

Logs were spitting "RenderFlex overflowed by 1.00 pixels on the
bottom" from album_card.dart whenever the library Albums tab or
artist detail album grid rendered. Cell height was computed as
cover + gap + title + artist + 4px slack, which assumes pixel-perfect
14sp/12sp line heights — Flutter's actual rendering with ascent/
descent + line-height multipliers wants one more pixel.

Bump slack from 4 to 8 in both grids. AlbumCard layout unchanged;
the warnings stop.

Otherwise the log shape is healthy now: prefetcher fires once per
library page emit (expected, one batch per pagination), cache misses
fetch sequentially with clean drift-write → re-emit cycles, and
album taps are single-round-trip cold-fetches followed by drift hits.
No more cycles of duplicate fetches.

flutter_client/lib/library/artist_detail_screen.dart

@@ -141,10 +141,11 @@ class ArtistDetailScreen extends ConsumerWidget {
                   (constraints.maxWidth - sidePad * 2 - gap * (cols - 1)) /
                       cols;
               // Card content: cover (cellW - 16) + 8 + title (≤2 lines
-              // ≈ 36) + small fudge. Artist line is suppressed in this
+              // ≈ 36) + slack. Artist line is suppressed in this
               // grid (showArtist: false) since the page header already
-              // names the artist.
-              final cellH = (cellW - 16) + 8 + 36 + 4;
+              // names the artist. Slack is generous on purpose — line-
+              // height variations would otherwise overflow by 1px.
+              final cellH = (cellW - 16) + 8 + 36 + 8;
               return GridView.builder(
                 shrinkWrap: true,
                 physics: const NeverScrollableScrollPhysics(),

flutter_client/lib/library/library_screen.dart

@@ -288,8 +288,11 @@ class _AlbumsTab extends ConsumerWidget {
                             gap * (cols - 1)) /
                         cols;
                     // cover (cellW - 16) + gap (8) + 2-line title (~36)
-                    // + artist line (~16) + small fudge.
-                    final cellH = (cellW - 16) + 8 + 36 + 16 + 4;
+                    // + artist line (~16) + slack. Slack is generous on
+                    // purpose — line-height + font scaling variations
+                    // would otherwise overflow the cell by a pixel
+                    // (logged as a noisy RenderFlex warning).
+                    final cellH = (cellW - 16) + 8 + 36 + 16 + 8;
                     return NotificationListener<ScrollNotification>(
                       onNotification: (n) {
                         if (n.metrics.pixels >=