chore(editor): update loading css vars (#12557)

Related to: [BS-3559](https://linear.app/affine-design/issue/BS-3559/ui-%E5%9B%BE%E7%89%87-loading-%E5%8F%98%E9%87%8F%E6%9B%B4%E6%96%B0)

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

- **Style**
  - Improved the appearance of image loading indicators by updating background and ring colors for a more consistent visual experience.

- **New Features**
  - Added customization options for the loading icon's ring color.

- **Chores**
  - Updated the "@toeverything/theme" dependency to version ^1.1.15 across multiple packages for improved consistency and compatibility.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/components/src/icons/loading.ts

@@ -4,10 +4,12 @@ import { html } from 'lit';
 export const LoadingIcon = ({
   size = '1em',
   progress = 0.2,
+  ringColor = cssVarV2('loading/background'),
   strokeColor = cssVarV2('loading/foreground'),
 }: {
   size?: string;
   progress?: number;
+  ringColor?: string;
   strokeColor?: string;
 } = {}) =>
   html`<svg
@@ -28,13 +30,7 @@ export const LoadingIcon = ({
         }
       }
     </style>
-    <circle
-      cx="12"
-      cy="12"
-      r="8"
-      stroke="${cssVarV2('loading/background')}"
-      stroke-width="4"
-    />
+    <circle cx="12" cy="12" r="8" stroke="${ringColor}" stroke-width="4" />
     <circle
       class="spinner"
       cx="12"