feat: add SkippedPackage model for tracking skipped/failed archives

Adds SkipReason enum (SIZE_LIMIT, DOWNLOAD_FAILED, EXTRACT_FAILED,
UPLOAD_FAILED) and SkippedPackage model with unique constraint on
(sourceChannelId, sourceMessageId). Reverse relations added to
TelegramAccount and TelegramChannel.

Note: Run `npx prisma migrate dev --name add-skipped-packages` when
database is available to create the migration.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prisma/schema.prisma

@@ -412,6 +412,7 @@ model TelegramAccount {
   channelMaps     AccountChannelMap[]
   ingestionRuns   IngestionRun[]
   fetchRequests   ChannelFetchRequest[]
+  skippedPackages SkippedPackage[]
 
   @@index([isActive])
   @@map("telegram_accounts")
@@ -430,6 +431,7 @@ model TelegramChannel {
 
   accountMaps     AccountChannelMap[]
   packages        Package[]
+  skippedPackages SkippedPackage[]
 
   @@index([type, isActive])
   @@index([category])
@@ -686,6 +688,39 @@ model ArchiveExtractRequest {
   @@map("archive_extract_requests")
 }
 
+// ───────────────────────────────────────
+// Skipped/Failed Archives
+// ───────────────────────────────────────
+
+enum SkipReason {
+  SIZE_LIMIT
+  DOWNLOAD_FAILED
+  EXTRACT_FAILED
+  UPLOAD_FAILED
+}
+
+model SkippedPackage {
+  id              String           @id @default(cuid())
+  fileName        String
+  fileSize        BigInt
+  reason          SkipReason
+  errorMessage    String?
+  sourceChannelId String
+  sourceChannel   TelegramChannel  @relation(fields: [sourceChannelId], references: [id], onDelete: Cascade)
+  sourceMessageId BigInt
+  sourceTopicId   BigInt?
+  isMultipart     Boolean          @default(false)
+  partCount       Int              @default(1)
+  accountId       String
+  account         TelegramAccount  @relation(fields: [accountId], references: [id], onDelete: Cascade)
+  createdAt       DateTime         @default(now())
+
+  @@unique([sourceChannelId, sourceMessageId])
+  @@index([reason])
+  @@index([accountId])
+  @@map("skipped_packages")
+}
+
 // ───────────────────────────────────────
 // Purchased Kickstarters
 // ───────────────────────────────────────