feat: initial CodeBoard monorepo scaffold

Turborepo monorepo with npm workspaces:
- apps/web: Next.js 14 frontend with Tailwind v4, SSE progress, doc viewer
- apps/worker: BullMQ job processor (clone → parse → LLM generate)
- packages/shared: TypeScript types
- packages/parser: Babel-based AST parser (JS/TS) + regex (Python)
- packages/llm: OpenAI/Anthropic provider abstraction + prompt pipeline
- packages/diagrams: Mermaid architecture & dependency graph generators
- packages/database: Prisma schema (PostgreSQL)
- Docker multi-stage build (web + worker targets)

All packages compile successfully with tsc and next build.

docker-compose.yml

@@ -0,0 +1,55 @@
+services:
+  web:
+    build:
+      context: .
+      target: web
+    ports:
+      - "3000:3000"
+    environment:
+      - DATABASE_URL=postgresql://codeboard:codeboard@db:5432/codeboard
+      - REDIS_URL=redis://redis:6379
+      - NEXTAUTH_URL=http://localhost:3000
+    depends_on:
+      - db
+      - redis
+    restart: always
+
+  worker:
+    build:
+      context: .
+      target: worker
+    environment:
+      - DATABASE_URL=postgresql://codeboard:codeboard@db:5432/codeboard
+      - REDIS_URL=redis://redis:6379
+      - OPENAI_API_KEY=${OPENAI_API_KEY:-}
+      - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY:-}
+      - LLM_MODEL=${LLM_MODEL:-}
+      - LLM_BASE_URL=${LLM_BASE_URL:-}
+    depends_on:
+      - db
+      - redis
+    restart: always
+
+  db:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: codeboard
+      POSTGRES_PASSWORD: codeboard
+      POSTGRES_DB: codeboard
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    ports:
+      - "5432:5432"
+    restart: always
+
+  redis:
+    image: redis:7-alpine
+    ports:
+      - "6379:6379"
+    volumes:
+      - redis_data:/data
+    restart: always
+
+volumes:
+  postgres_data:
+  redis_data: