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.

PLAN.md

@@ -776,7 +776,7 @@ cannot submit; three-way admin filter.
     reusable **HoldConfirm** press-and-hold control (MakeMove 🏁 + game-action confirms);
     board **zoom reworked** to a width-based zoom in a fixed viewport (real native
     scroll, double-tap; pinch/swipe dropped) with constant `cqw` labels, corner-letter
-    tiles, contrasting grid lines, last-word dark-tile highlight, and a Settings
+    tiles, last-word dark-tile highlight, and a Settings
     **bonus-label style** (beginner/
     classic/none); **hint lays its tiles on the board** (no spend when no move — a new
     `no_hint_available` result code); the history opens as an in-place **slide-down**