fix(themes): theme wallpapers dont apply on firefox

src/plugins/built-in/themes/themeImageUrl.ts

@@ -0,0 +1,38 @@
+/**
+ * Theme decorative images must use data URLs instead of blob URLs on Firefox:
+ * blob: URLs are tied to the origin where createObjectURL ran (page), while
+ * settings UI runs in extension shadow DOM (moz-extension://).
+ */
+export function blobToDataUrl(blob: Blob): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onloadend = () => {
+      if (typeof reader.result === "string") {
+        resolve(reader.result);
+      } else {
+        reject(new Error("FileReader did not return a string"));
+      }
+    };
+    reader.onerror = () =>
+      reject(reader.error ?? new Error("FileReader failed"));
+    reader.readAsDataURL(blob);
+  });
+}
+
+/** Base64 payload only (no `data:…;base64,` prefix) for the page-context bridge. */
+export function blobToBase64Data(blob: Blob): Promise<string> {
+  return blobToDataUrl(blob).then((dataUrl) => {
+    const comma = dataUrl.indexOf(",");
+    return comma >= 0 ? dataUrl.slice(comma + 1) : dataUrl;
+  });
+}
+
+export function themeCssUrlValue(url: string): string {
+  return `url("${url.replace(/"/g, "%22")}")`;
+}
+
+export function releaseThemeImageUrl(url: string): void {
+  if (url.startsWith("blob:")) {
+    URL.revokeObjectURL(url);
+  }
+}