feat(knowledge): add database schema for Knowledge Module

Implements KNOW-001
- KnowledgeEntry, Version, Link, Tag, Embedding models
- Full indexes and constraints
- Seed data for testing

apps/api/prisma/schema.prisma

@@ -96,6 +96,18 @@ enum AgentStatus {
   TERMINATED
 }
 
+enum EntryStatus {
+  DRAFT
+  PUBLISHED
+  ARCHIVED
+}
+
+enum Visibility {
+  PRIVATE
+  WORKSPACE
+  PUBLIC
+}
+
 // ============================================
 // MODELS
 // ============================================
@@ -138,19 +150,21 @@ model Workspace {
   updatedAt DateTime @updatedAt @map("updated_at") @db.Timestamptz
 
   // Relations
-  owner            User              @relation("WorkspaceOwner", fields: [ownerId], references: [id], onDelete: Cascade)
-  members          WorkspaceMember[]
-  tasks            Task[]
-  events           Event[]
-  projects         Project[]
-  activityLogs     ActivityLog[]
-  memoryEmbeddings MemoryEmbedding[]
-  domains          Domain[]
-  ideas            Idea[]
-  relationships    Relationship[]
-  agents           Agent[]
-  agentSessions    AgentSession[]
-  userLayouts      UserLayout[]
+  owner              User              @relation("WorkspaceOwner", fields: [ownerId], references: [id], onDelete: Cascade)
+  members            WorkspaceMember[]
+  tasks              Task[]
+  events             Event[]
+  projects           Project[]
+  activityLogs       ActivityLog[]
+  memoryEmbeddings   MemoryEmbedding[]
+  domains            Domain[]
+  ideas              Idea[]
+  relationships      Relationship[]
+  agents             Agent[]
+  agentSessions      AgentSession[]
+  userLayouts        UserLayout[]
+  knowledgeEntries   KnowledgeEntry[]
+  knowledgeTags      KnowledgeTag[]
 
   @@index([ownerId])
   @@map("workspaces")
@@ -605,3 +619,131 @@ model Verification {
   @@index([identifier])
   @@map("verifications")
 }
+
+// ============================================
+// KNOWLEDGE MODULE
+// ============================================
+
+model KnowledgeEntry {
+  id          String      @id @default(uuid()) @db.Uuid
+  workspaceId String      @map("workspace_id") @db.Uuid
+  workspace   Workspace   @relation(fields: [workspaceId], references: [id], onDelete: Cascade)
+
+  // Identity
+  slug        String
+  title       String
+  
+  // Content
+  content     String      @db.Text
+  contentHtml String?     @map("content_html") @db.Text
+  summary     String?
+  
+  // Status
+  status      EntryStatus @default(DRAFT)
+  visibility  Visibility  @default(PRIVATE)
+  
+  // Audit
+  createdAt   DateTime    @default(now()) @map("created_at") @db.Timestamptz
+  updatedAt   DateTime    @updatedAt @map("updated_at") @db.Timestamptz
+  createdBy   String      @map("created_by") @db.Uuid
+  updatedBy   String      @map("updated_by") @db.Uuid
+  
+  // Relations
+  tags          KnowledgeEntryTag[]
+  outgoingLinks KnowledgeLink[]     @relation("SourceEntry")
+  incomingLinks KnowledgeLink[]     @relation("TargetEntry")
+  versions      KnowledgeEntryVersion[]
+  embedding     KnowledgeEmbedding?
+  
+  @@unique([workspaceId, slug])
+  @@index([workspaceId, status])
+  @@index([workspaceId, updatedAt])
+  @@index([createdBy])
+  @@index([updatedBy])
+  @@map("knowledge_entries")
+}
+
+model KnowledgeEntryVersion {
+  id         String         @id @default(uuid()) @db.Uuid
+  entryId    String         @map("entry_id") @db.Uuid
+  entry      KnowledgeEntry @relation(fields: [entryId], references: [id], onDelete: Cascade)
+  
+  version    Int
+  title      String
+  content    String         @db.Text
+  summary    String?
+  
+  createdAt  DateTime       @default(now()) @map("created_at") @db.Timestamptz
+  createdBy  String         @map("created_by") @db.Uuid
+  changeNote String?        @map("change_note")
+  
+  @@unique([entryId, version])
+  @@index([entryId, version])
+  @@map("knowledge_entry_versions")
+}
+
+model KnowledgeLink {
+  id        String         @id @default(uuid()) @db.Uuid
+  
+  sourceId  String         @map("source_id") @db.Uuid
+  source    KnowledgeEntry @relation("SourceEntry", fields: [sourceId], references: [id], onDelete: Cascade)
+  
+  targetId  String         @map("target_id") @db.Uuid
+  target    KnowledgeEntry @relation("TargetEntry", fields: [targetId], references: [id], onDelete: Cascade)
+  
+  // Link metadata
+  linkText  String         @map("link_text")
+  context   String?
+  
+  createdAt DateTime       @default(now()) @map("created_at") @db.Timestamptz
+  
+  @@unique([sourceId, targetId])
+  @@index([sourceId])
+  @@index([targetId])
+  @@map("knowledge_links")
+}
+
+model KnowledgeTag {
+  id          String @id @default(uuid()) @db.Uuid
+  workspaceId String @map("workspace_id") @db.Uuid
+  workspace   Workspace @relation(fields: [workspaceId], references: [id], onDelete: Cascade)
+  
+  name        String
+  slug        String
+  color       String?
+  description String?
+  
+  entries     KnowledgeEntryTag[]
+  
+  @@unique([workspaceId, slug])
+  @@index([workspaceId])
+  @@map("knowledge_tags")
+}
+
+model KnowledgeEntryTag {
+  entryId String         @map("entry_id") @db.Uuid
+  entry   KnowledgeEntry @relation(fields: [entryId], references: [id], onDelete: Cascade)
+  
+  tagId   String         @map("tag_id") @db.Uuid
+  tag     KnowledgeTag   @relation(fields: [tagId], references: [id], onDelete: Cascade)
+  
+  @@id([entryId, tagId])
+  @@index([entryId])
+  @@index([tagId])
+  @@map("knowledge_entry_tags")
+}
+
+model KnowledgeEmbedding {
+  id        String         @id @default(uuid()) @db.Uuid
+  entryId   String         @unique @map("entry_id") @db.Uuid
+  entry     KnowledgeEntry @relation(fields: [entryId], references: [id], onDelete: Cascade)
+  
+  embedding Unsupported("vector(1536)")
+  model     String
+  
+  createdAt DateTime       @default(now()) @map("created_at") @db.Timestamptz
+  updatedAt DateTime       @updatedAt @map("updated_at") @db.Timestamptz
+  
+  @@index([entryId])
+  @@map("knowledge_embeddings")
+}