feat: add initial backend and frontend structure with models, DTOs, and WebSocket events

apps/backend/prisma/models/character.prisma

@@ -0,0 +1,56 @@
+// Character model and character knowledge
+
+enum ImportSourceType {
+  file
+  url
+  manual
+}
+
+enum ImportStatus {
+  pending
+  processing
+  completed
+  failed
+}
+
+model Character {
+  id                  String   @id @default(uuid())
+  name                String
+  avatarUrl           String?
+  personalityPrompt   String
+  attributes          Json     @default("{}")
+  config              Json     @default("{}")
+  isPublic            Boolean  @default(false)
+  createdAt           DateTime @default(now())
+  updatedAt           DateTime @updatedAt
+
+  userId              String
+  user                User                @relation(fields: [userId], references: [id], onDelete: Cascade)
+  conversations       Conversation[]
+  knowledgeSources    CharacterKnowledge[]
+  vectorMemories      VectorMemory[]
+
+  @@index([userId])
+  @@index([name])
+}
+
+model CharacterKnowledge {
+  id              String           @id @default(uuid())
+  name            String
+  sourceType      ImportSourceType
+  sourceName      String
+  mimeType        String?
+  fileSize        BigInt?
+  rawContent      String?
+  status          ImportStatus     @default(pending)
+  processingInfo  Json?
+  createdAt       DateTime         @default(now())
+  updatedAt       DateTime         @updatedAt
+
+  characterId     String
+  character       Character        @relation(fields: [characterId], references: [id], onDelete: Cascade)
+  vectorMemories  VectorMemory[]
+
+  @@index([characterId])
+  @@index([status])
+}