fix: resolve progress update errors and use dynamic page calculation

- reader-navigation.ts: add fallback for mediaItemId from page URL
- reader-navigation.ts: use getCurrentPageFromScroll for accurate page tracking
- reader-navigation.ts: use pageCalculationResult.totalPages for total
- reader-services.ts: validate mediaItemId before API call
- reader-services.ts: avoid double body consumption by checking response.ok

web/src/reader/core/reader-services.ts

@@ -9,11 +9,19 @@ export async function updateReadingProgress(
   mediaItemId: string,
   progress: ReadingProgress,
 ): Promise<void> {
+  if (!mediaItemId || mediaItemId === "undefined") {
+    console.warn("Skipping progress update - no valid mediaItemId");
+    return;
+  }
   const response = await apiPut(
     `/media-items/${mediaItemId}/progress`,
     progress,
   );
-  await response.json();
+  if (!response.ok) {
+    const errorText = await response.text();
+    console.warn("Progress update failed:", response.status, errorText);
+    return;
+  }
 }
 
 export function getChapterNavigation(chapters: any[]) {