feat(backend): Day 5 - backend basic architecture setup completed

backend/prisma/schema.prisma

@@ -0,0 +1,182 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "postgresql"
+  url      = env("DATABASE_URL")
+}
+
+// ==================== 用户模块 ====================
+
+model User {
+  id            String   @id @default(uuid())
+  email         String   @unique
+  password      String
+  name          String?
+  avatarUrl     String?  @map("avatar_url")
+  
+  role          String   @default("user")
+  status        String   @default("active")
+  
+  kbQuota       Int      @default(3) @map("kb_quota")
+  kbUsed        Int      @default(0) @map("kb_used")
+  
+  trialEndsAt   DateTime? @map("trial_ends_at")
+  isTrial       Boolean  @default(true) @map("is_trial")
+  
+  lastLoginAt   DateTime? @map("last_login_at")
+  createdAt     DateTime @default(now()) @map("created_at")
+  updatedAt     DateTime @updatedAt @map("updated_at")
+  
+  projects      Project[]
+  conversations Conversation[]
+  knowledgeBases KnowledgeBase[]
+  documents     Document[]
+  adminLogs     AdminLog[]
+  
+  @@index([email])
+  @@index([status])
+  @@index([createdAt])
+  @@map("users")
+}
+
+// ==================== 项目模块 ====================
+
+model Project {
+  id                String   @id @default(uuid())
+  userId            String   @map("user_id")
+  name              String
+  description       String   @db.Text
+  conversationCount Int      @default(0) @map("conversation_count")
+  
+  createdAt         DateTime @default(now()) @map("created_at")
+  updatedAt         DateTime @updatedAt @map("updated_at")
+  
+  user              User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+  conversations     Conversation[]
+  
+  @@index([userId])
+  @@index([createdAt])
+  @@map("projects")
+}
+
+// ==================== 对话模块 ====================
+
+model Conversation {
+  id           String   @id @default(uuid())
+  userId       String   @map("user_id")
+  projectId    String?  @map("project_id")
+  agentId      String   @map("agent_id")
+  title        String
+  modelName    String   @default("deepseek-v3") @map("model_name")
+  messageCount Int      @default(0) @map("message_count")
+  totalTokens  Int      @default(0) @map("total_tokens")
+  
+  createdAt    DateTime @default(now()) @map("created_at")
+  updatedAt    DateTime @updatedAt @map("updated_at")
+  
+  user         User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+  project      Project? @relation(fields: [projectId], references: [id], onDelete: Cascade)
+  messages     Message[]
+  
+  @@index([userId])
+  @@index([projectId])
+  @@index([agentId])
+  @@index([createdAt])
+  @@map("conversations")
+}
+
+model Message {
+  id             String   @id @default(uuid())
+  conversationId String   @map("conversation_id")
+  role           String
+  content        String   @db.Text
+  metadata       Json?
+  tokens         Int?
+  isPinned       Boolean  @default(false) @map("is_pinned")
+  
+  createdAt      DateTime @default(now()) @map("created_at")
+  
+  conversation   Conversation @relation(fields: [conversationId], references: [id], onDelete: Cascade)
+  
+  @@index([conversationId])
+  @@index([createdAt])
+  @@index([isPinned])
+  @@map("messages")
+}
+
+// ==================== 知识库模块 ====================
+
+model KnowledgeBase {
+  id             String   @id @default(uuid())
+  userId         String   @map("user_id")
+  name           String
+  description    String?
+  difyDatasetId  String   @map("dify_dataset_id")
+  fileCount      Int      @default(0) @map("file_count")
+  totalSizeBytes BigInt   @default(0) @map("total_size_bytes")
+  
+  createdAt      DateTime @default(now()) @map("created_at")
+  updatedAt      DateTime @updatedAt @map("updated_at")
+  
+  user           User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+  documents      Document[]
+  
+  @@index([userId])
+  @@index([difyDatasetId])
+  @@map("knowledge_bases")
+}
+
+model Document {
+  id              String   @id @default(uuid())
+  kbId            String   @map("kb_id")
+  userId          String   @map("user_id")
+  filename        String
+  fileType        String   @map("file_type")
+  fileSizeBytes   BigInt   @map("file_size_bytes")
+  fileUrl         String   @map("file_url")
+  difyDocumentId  String   @map("dify_document_id")
+  status          String   @default("uploading")
+  progress        Int      @default(0)
+  errorMessage    String?  @map("error_message")
+  segmentsCount   Int?     @map("segments_count")
+  tokensCount     Int?     @map("tokens_count")
+  
+  uploadedAt      DateTime @default(now()) @map("uploaded_at")
+  processedAt     DateTime? @map("processed_at")
+  
+  knowledgeBase   KnowledgeBase @relation(fields: [kbId], references: [id], onDelete: Cascade)
+  user            User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+  
+  @@index([kbId])
+  @@index([userId])
+  @@index([status])
+  @@index([difyDocumentId])
+  @@map("documents")
+}
+
+// ==================== 运营管理模块 ====================
+
+model AdminLog {
+  id           Int      @id @default(autoincrement())
+  adminId      String   @map("admin_id")
+  action       String
+  resourceType String?  @map("resource_type")
+  resourceId   String?  @map("resource_id")
+  details      Json?
+  ipAddress    String?  @map("ip_address")
+  userAgent    String?  @map("user_agent")
+  
+  createdAt    DateTime @default(now()) @map("created_at")
+  
+  admin        User     @relation(fields: [adminId], references: [id], onDelete: Cascade)
+  
+  @@index([adminId])
+  @@index([createdAt])
+  @@index([action])
+  @@map("admin_logs")
+}