feat(ui): batch of UI polish tweaks

- admin dashboard "Users" count excludes robots (CountUsers, humans only)
- lobby finished-game delete reveal: background matches header/tab-bar (--bg-elev)
- mobile: swipe up on the zoom-out board (no staged tiles) shuffles the rack
- lobby: status icons -25%, game-row top/bottom padding halved
- toast: info tier drifts up ~a tab-bar height while fading over 2s and dismisses
  on tap; error tier unchanged
- game: confirm-move button stays pinned at the right edge; rack tiles shrink to
  fit so a full rack never overflows onto it
- telegram: a successful invite-link redeem shows a welcome window pointing at the bot
- settings: remove the grid-lines toggle; the board is always a gapless checkerboard
- settings/comms hubs: the selected tab highlight wraps icon + label as a pill

Docs: UI_DESIGN (toast, board surface, selected tab), PLAN; e2e updated for the
removed grid-lines toggle.

ui/src/game/Board.svelte

@@ -18,7 +18,6 @@
     landscape,
     variant,
     labelMode,
-    lines,
     locale,
     focus,
     recenter,
@@ -41,8 +40,6 @@
     landscape: boolean;
     variant: Variant;
     labelMode: BoardLabelMode;
-    /** Draw 1px grid lines between cells; when false the board is a gapless checkerboard. */
-    lines: boolean;
     locale: Locale;
     focus: { row: number; col: number } | null;
     /** A monotonic nonce the parent bumps to request a scroll to `focus` even when the zoom state
@@ -234,7 +231,7 @@
 
 <div class="viewport" class:zoomed class:land={landscape} bind:this={viewport}>
   <div class="scaler" class:land={landscape} style="--z: {z};">
-    <div class="grid" class:gridless={!lines}>
+    <div class="grid">
       {#each board as rowCells, r (r)}
         {#each rowCells as cell, c (c)}
           {@const p = pending.get(key(r, c))}
@@ -311,18 +308,21 @@
       width 0.25s ease,
       height 0.25s ease;
   }
+  /* A gapless checkerboard with no grid lines (the board has no lined variant): plain cells
+     alternate shades and tiles get rounded corners plus a soft right-side shadow so adjacent
+     gapless tiles still read as separate pieces. */
   .grid {
     display: grid;
     grid-template-columns: repeat(15, 1fr);
-    gap: 1px;
-    background: var(--cell-line);
-    padding: 1px;
+    gap: 0;
+    background: var(--board-bg);
+    padding: 0;
   }
   .cell {
     position: relative;
     aspect-ratio: 1;
     border: none;
-    border-radius: 1px;
+    border-radius: 0;
     background: var(--cell-bg);
     color: var(--prem-text);
     /* No mobile tap flash on a cell tap (parity with the web click; the only intentional
@@ -344,11 +344,20 @@
   .cell.dl {
     background: var(--prem-dl);
   }
+  .cell.dark {
+    /* A gentle checkerboard tint: enough to read the alternation without competing with the
+       bonus cells, standing in for the grid lines that once separated the cells. Lightened
+       from a stronger mix that looked too contrasty in light theme. */
+    background: color-mix(in srgb, var(--cell-bg) 94%, #000);
+  }
   .cell.filled,
   .cell.pending {
     background: var(--tile-bg);
     color: var(--tile-text);
-    box-shadow: inset 0 -2px 0 var(--tile-edge);
+    border-radius: 4px;
+    box-shadow:
+      inset 0 -2px 0 var(--tile-edge),
+      2px 0 3px -1px rgba(0, 0, 0, 0.4);
   }
   .cell.pending {
     background: var(--tile-pending);
@@ -356,30 +365,6 @@
        board) instead of the touch starting a board pan. */
     touch-action: none;
   }
-  /* Lines-off variant: a gapless checkerboard. The 1px grid gaps (and the cell-line they
-     reveal) collapse, saving ~14px of board width; plain cells alternate shades, and tiles
-     get rounded corners and a soft right-side shadow so adjacent gapless tiles still read
-     as separate pieces. */
-  .grid.gridless {
-    gap: 0;
-    padding: 0;
-    background: var(--board-bg);
-  }
-  .grid.gridless .cell {
-    border-radius: 0;
-  }
-  .grid.gridless .cell.dark {
-    /* A gentle checkerboard tint: enough to read the alternation without competing with the
-       bonus cells. Lightened from a stronger mix that looked too contrasty in light theme. */
-    background: color-mix(in srgb, var(--cell-bg) 94%, #000);
-  }
-  .grid.gridless .cell.filled,
-  .grid.gridless .cell.pending {
-    border-radius: 4px;
-    box-shadow:
-      inset 0 -2px 0 var(--tile-edge),
-      2px 0 3px -1px rgba(0, 0, 0, 0.4);
-  }
   .cell.droptarget {
     /* The cell a carried tile is aimed at: an accent ring plus a light accent wash, so the
        target reads clearly while dragging without obscuring the bonus label underneath. */