feat: member portal Sprint 5 — onboarding portal experience + restore Thread schema

- Redesign onboarding into a 5-step wizard: welcome → phone → consent → code → done
- Progress bar, human-readable consent scopes (INGEST/ARCHIVE/REPLICATE/DISPLAY) with descriptions
- Resend-code action, back navigation, indigo theme matching member portal
- "Done" step introduces portal features (digests, events, privacy) with CTA
- Onboard page shell: rounded card, policy footer
- Restore Thread model + Message.expiresAt/quotedPlatformMsgId/threadId + RAW/DNC statuses to schema.prisma (wiped by prior reset; matches existing add_hybrid_ai_architecture migration) — unblocks ThreadsModule registration

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

apps/api/prisma/schema.prisma

@@ -91,6 +91,7 @@ model Tenant {
   digestConfig   DigestConfig?
   digests        Digest[]
   events         Event[]
+  threads        Thread[]
 }
 
 enum AdminRole {
@@ -235,6 +236,7 @@ model Group {
   consents        ConsentRecord[]
   claimTokens     GroupClaimToken[]
   groupAccesses   GroupAccess[]
+  threads         Thread[]
 
   @@unique([platform, platformId])
   @@index([accountId])
@@ -247,37 +249,62 @@ model Group {
 // ============================================================================
 
 model Message {
-  id                 String        @id @default(cuid())
-  tenantId           String
-  tenant             Tenant        @relation(fields: [tenantId], references: [id])
-  platform           String
-  platformMsgId      String
-  sourceGroupId      String
-  sourceGroup        Group         @relation(fields: [sourceGroupId], references: [id])
-  senderJid          String
-  senderName         String?
-  senderTowerUserId  String?
-  senderTowerUser    TowerUser?    @relation("senderTowerUser", fields: [senderTowerUserId], references: [id])
-  content            String
-  mediaUrl           String?
-  tags               String[]
-  status             MessageStatus @default(PENDING)
-  createdAt          DateTime      @default(now())
-  updatedAt          DateTime      @updatedAt
+  id                  String        @id @default(cuid())
+  tenantId            String
+  tenant              Tenant        @relation(fields: [tenantId], references: [id])
+  platform            String
+  platformMsgId       String
+  sourceGroupId       String
+  sourceGroup         Group         @relation(fields: [sourceGroupId], references: [id])
+  senderJid           String
+  senderName          String?
+  senderTowerUserId   String?
+  senderTowerUser     TowerUser?    @relation("senderTowerUser", fields: [senderTowerUserId], references: [id])
+  content             String
+  mediaUrl            String?
+  tags                String[]
+  status              MessageStatus @default(PENDING)
+  expiresAt           DateTime?
+  quotedPlatformMsgId String?
+  threadId            String?
+  thread              Thread?       @relation(fields: [threadId], references: [id])
+  createdAt           DateTime      @default(now())
+  updatedAt           DateTime      @updatedAt
 
   approval Approval?
 
   @@unique([platform, platformMsgId])
   @@index([tenantId])
   @@index([senderTowerUserId])
+  @@index([status, expiresAt])
+  @@index([threadId])
 }
 
 enum MessageStatus {
+  RAW
   PENDING
   APPROVED
   REJECTED
   DISTRIBUTED
   ARCHIVED
+  DNC
+}
+
+model Thread {
+  id             String   @id @default(cuid())
+  tenantId       String
+  tenant         Tenant   @relation(fields: [tenantId], references: [id])
+  sourceGroupId  String
+  sourceGroup    Group    @relation(fields: [sourceGroupId], references: [id])
+  lastActivityAt DateTime @default(now())
+  messageCount   Int      @default(0)
+  topic          String?
+  createdAt      DateTime @default(now())
+
+  messages Message[]
+
+  @@index([tenantId])
+  @@index([sourceGroupId, lastActivityAt])
 }
 
 model Approval {