injectStyles function

function injectStyles(): void {
  if (document.getElementById("fill-all-effect-pin-styles")) return;
  const style = document.createElement("style");
  style.id = "fill-all-effect-pin-styles";
  style.textContent = `
    .${PIN_CLASS} {
      position: fixed;
      z-index: 2147483646;
      pointer-events: none;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    .${PIN_CLASS}__dot {
      width: 14px;
      height: 14px;
      background: #e53e3e;
      border: 2px solid #fff;
      border-radius: 50%;
      box-shadow: 0 0 0 0 rgba(229,62,62,0.5);
      animation: fill-all-pin-pulse 1.2s ease infinite;
    }
    .${PIN_CLASS}__note {
      margin-top: 4px;
      padding: 3px 8px;
      background: #e53e3e;
      color: #fff;
      font-size: 12px;
      font-family: system-ui, sans-serif;
      border-radius: 4px;
      white-space: nowrap;
    }
    @keyframes fill-all-pin-pulse {
      0%   { box-shadow: 0 0 0 0 rgba(229,62,62,0.5); }
      70%  { box-shadow: 0 0 0 10px rgba(229,62,62,0); }
      100% { box-shadow: 0 0 0 0 rgba(229,62,62,0); }
    }
  `;
  document.head.appendChild(style);
}