fix(astro): Convert SDK init file import paths to POSIX paths (#9336)

Convert init file import paths to POSIX paths to ensure Vite can resolve the path to the file correctly when the import statement to inject the file into the client and browser bundles is added.

packages/astro/src/integration/snippets.ts

@@ -1,10 +1,12 @@
+import * as path from 'path';
+
 import type { SentryOptions } from './types';
 
 /**
  * Creates a snippet that imports a Sentry.init file.
  */
 export function buildSdkInitFileImportSnippet(filePath: string): string {
-  return `import "${filePath}";`;
+  return `import "${pathToPosix(filePath)}";`;
 }
 
 /**
@@ -69,3 +71,7 @@ const buildClientIntegrations = (options: SentryOptions): string => {
 
   return integrations.join(', ');
 };
+
+function pathToPosix(originalPath: string): string {
+  return originalPath.split(path.sep).join(path.posix.sep);
+}