refactor: remove versioning from reading progress implementation

- Remove 'ver' field from ReadingProgressContent interface
- Remove ver: '1' from saveReadingPosition function
- Update PROGRESS_CACHE_KEY to remove v1 suffix

src/services/readingPositionService.ts

@@ -19,7 +19,6 @@ export interface ReadingProgressContent {
   progress: number // 0-1 scroll progress
   ts?: number // Unix timestamp (optional, for display)
   loc?: number // Optional: pixel position
-  ver?: string // Schema version
 }
 
 // Helper to extract and parse reading progress from event (kind 39802)
@@ -117,8 +116,7 @@ export async function saveReadingPosition(
   const progressContent: ReadingProgressContent = {
     progress: position.position,
     ts: position.timestamp,
-    loc: position.scrollTop,
-    ver: '1'
+    loc: position.scrollTop
   }
   
   const tags = generateProgressTags(articleIdentifier)

src/services/readingProgressController.ts

@@ -13,7 +13,7 @@ type ProgressMapCallback = (progressMap: Map<string, number>) => void
 type LoadingCallback = (loading: boolean) => void
 
 const LAST_SYNCED_KEY = 'reading_progress_last_synced'
-const PROGRESS_CACHE_KEY = 'reading_progress_cache_v1'
+const PROGRESS_CACHE_KEY = 'reading_progress_cache'
 
 /**
  * Shared reading progress controller