feat: add knowledge version history (closes #75, closes #76)

- Added EntryVersion model with author relation
- Implemented automatic versioning on entry create/update
- Added API endpoints for version history:
  - GET /api/knowledge/entries/:slug/versions - list versions
  - GET /api/knowledge/entries/:slug/versions/:version - get specific
  - POST /api/knowledge/entries/:slug/restore/:version - restore version
- Created VersionHistory.tsx component with timeline view
- Added History tab to entry detail page
- Supports version viewing and restoring
- Includes comprehensive tests for version operations
- All TypeScript types are explicit and type-safe

apps/api/prisma/schema.prisma

@@ -130,21 +130,22 @@ model User {
   updatedAt      DateTime @updatedAt @map("updated_at") @db.Timestamptz
 
   // Relations
-  ownedWorkspaces      Workspace[]       @relation("WorkspaceOwner")
-  workspaceMemberships WorkspaceMember[]
-  teamMemberships      TeamMember[]
-  assignedTasks        Task[]            @relation("TaskAssignee")
-  createdTasks         Task[]            @relation("TaskCreator")
-  createdEvents        Event[]           @relation("EventCreator")
-  createdProjects      Project[]         @relation("ProjectCreator")
-  activityLogs         ActivityLog[]
-  sessions             Session[]
-  accounts             Account[]
-  ideas                Idea[]            @relation("IdeaCreator")
-  relationships        Relationship[]    @relation("RelationshipCreator")
-  agentSessions        AgentSession[]
-  userLayouts          UserLayout[]
-  userPreference       UserPreference?
+  ownedWorkspaces         Workspace[]              @relation("WorkspaceOwner")
+  workspaceMemberships    WorkspaceMember[]
+  teamMemberships         TeamMember[]
+  assignedTasks           Task[]                   @relation("TaskAssignee")
+  createdTasks            Task[]                   @relation("TaskCreator")
+  createdEvents           Event[]                  @relation("EventCreator")
+  createdProjects         Project[]                @relation("ProjectCreator")
+  activityLogs            ActivityLog[]
+  sessions                Session[]
+  accounts                Account[]
+  ideas                   Idea[]                   @relation("IdeaCreator")
+  relationships           Relationship[]           @relation("RelationshipCreator")
+  agentSessions           AgentSession[]
+  userLayouts             UserLayout[]
+  userPreference          UserPreference?
+  knowledgeEntryVersions  KnowledgeEntryVersion[]  @relation("EntryVersionAuthor")
 
   @@map("users")
 }
@@ -737,6 +738,7 @@ model KnowledgeEntryVersion {
 
   createdAt  DateTime @default(now()) @map("created_at") @db.Timestamptz
   createdBy  String   @map("created_by") @db.Uuid
+  author     User     @relation("EntryVersionAuthor", fields: [createdBy], references: [id])
   changeNote String?  @map("change_note")
 
   @@unique([entryId, version])