fix(editor): edgeless can't slider with finger (#15091)

fix bug edgeless can't slider with finger 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added mobile immersive edgeless mode with dynamic chrome auto-hide and
tap-gesture controls.
  * Added a mobile zoom ruler UI for edgeless.
* **Bug Fixes**
* Improved iOS rendering/zoom by applying low-zoom survival behavior,
gesture-aware refresh deferral, and effective-DPR canvas scaling.
* Fixed iOS webview zoom/bounce and process-termination reload behavior.
  * Improved placeholder styling with theme-aware colors.
* **Chores**
  * Updated local ignore rules and iOS app build/version configuration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DarkSky <darksky2048@gmail.com>

blocksuite/affine/shared/src/theme/index.ts

@@ -1 +1,2 @@
 export * from './css-variables.js';
+export * from './placeholder-style.js';

blocksuite/affine/shared/src/theme/placeholder-style.ts

@@ -0,0 +1,19 @@
+import { ColorScheme } from '@blocksuite/affine-model';
+
+export function inferColorSchemeFromThemeMode(
+  themeMode?: string | null
+): ColorScheme {
+  return themeMode === 'dark' ? ColorScheme.Dark : ColorScheme.Light;
+}
+
+export function getAffinePlaceholderFillColor(colorScheme: ColorScheme) {
+  return colorScheme === ColorScheme.Dark
+    ? 'rgba(255, 255, 255, 0.08)'
+    : 'rgba(0, 0, 0, 0.04)';
+}
+
+export function getAffinePlaceholderStrokeColor(colorScheme: ColorScheme) {
+  return colorScheme === ColorScheme.Dark
+    ? 'rgba(255, 255, 255, 0.04)'
+    : 'rgba(0, 0, 0, 0.02)';
+}