feat: implement authentication control with support for BYO API keys, episode deduplication, and a task queue for async processing.

prisma/schema.prisma

@@ -11,9 +11,14 @@ model Episode {
   id              String      @id @default(cuid())
   title           String
   originalContent String
+  contentHash     String?     // SHA-256 for deduplication
   scriptContent   String?
   mode            String      @default("VERBATIM") // VERBATIM | FEYNMAN | DUAL_HOST
-  status          String      @default("PENDING")  // PENDING | PROCESSING | READY | FAILED
+  targetLanguage  String      @default("auto")     // auto | zh | en
+  status          String      @default("QUEUED")   // QUEUED | PROCESSING | READY | FAILED
+  retryCount      Int         @default(0)
+  maxRetries      Int         @default(3)
+  nextAttemptAt   DateTime?
   errorMessage    String?
   durationSeconds Float?
   audioUrl        String?
@@ -22,6 +27,8 @@ model Episode {
   stages          StageItem[]
   createdAt       DateTime    @default(now())
   updatedAt       DateTime    @updatedAt
+
+  @@index([contentHash])
 }
 
 model StageItem {