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/e2e/game.spec.ts

@@ -123,16 +123,15 @@ test('a pending tile recalls on double-tap, not on a single tap', async ({ page
   await expect(page.locator('[data-cell].pending')).toHaveCount(0);
 });
 
-test('the board is a gapless checkerboard by default; grid lines toggle in Settings', async ({ page }) => {
+test('the board is always a gapless checkerboard; no grid-lines setting', async ({ page }) => {
   await openGame(page);
-  await expect(page.locator('.grid.gridless')).toBeVisible(); // lines off by default
-
-  await page.evaluate(() => (location.hash = '/settings'));
-  await page.locator('.gridlines input').check(); // turn grid lines on
-  await page.evaluate(() => (location.hash = '/game/g1'));
-
   await expect(page.locator('.grid')).toBeVisible();
-  await expect(page.locator('.grid.gridless')).toHaveCount(0);
+  // The board has no lined variant any more: its cells sit flush, with no inter-cell gap.
+  await expect(page.locator('.grid')).toHaveCSS('column-gap', '0px');
+
+  // Settings no longer offers a grid-lines toggle.
+  await page.evaluate(() => (location.hash = '/settings'));
+  await expect(page.locator('.gridlines')).toHaveCount(0);
 });
 
 test('shuffle reorders the rack but keeps the same tiles', async ({ page }) => {