Mark prd.json status as completed

All 23 stories (US-001 through US-023) are now complete.
Updated status from "in_progress" to "completed".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Yeachan-Heo

prd.json

@@ -336,6 +336,6 @@
     "completedStories": ["US-001", "US-002", "US-003", "US-004", "US-005", "US-006", "US-007", "US-008", "US-009", "US-010", "US-011", "US-012", "US-013", "US-014", "US-015", "US-016", "US-017", "US-018", "US-019", "US-020", "US-021", "US-022", "US-023"],
     "inProgressStories": [],
     "totalStories": 23,
-    "status": "in_progress"
+    "status": "completed"
   }
 }