feat(float): rebuild right floating buttons 1:1 with reference theme

- Storage: aksrt_floating_buttons now uses reference float_btn shape
  (fixed 8 sortable types, more-buttons group); single source of
  defaults/sanitize in AKSRT\Settings\FloatButtons
- Admin SPA: CSF-parity page split into components/floating/*
- Frontend: aksrt_float_right() on wp_footer mirrors zib_float_right()
  (wp_is_mobile, PC tooltip, toggle-theme, ontop/scrollTopTo, qrcode,
  wechat/qq, pay_vip, add, more)
- CSS: floating-buttons.css rewritten from reference rules; legacy float
  rules removed from main/part/shell/overlay-primitives
- Remove dead code: reorder route/API, get_floating_buttons_items,
  floatingSchema, floatActionsId, float-theme-toggle bindings,
  common/floating.css, aksrt-runtime-win.php, .aksrt-float-btn

assets/css/frontend/footer/shell.css

@@ -255,15 +255,3 @@
     transform: translateX(-50%);
   }
 }
-
-/* Float right buttons shell (kept from prior shell) */
-#float-right-btns.float-right,
-.float-right {
-  position: fixed;
-  right: 16px;
-  bottom: 60px;
-  z-index: 1030;
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-}