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.

apps/worker/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@codeboard/worker",
+  "version": "0.0.1",
+  "private": true,
+  "scripts": {
+    "build": "tsc",
+    "clean": "rm -rf dist",
+    "dev": "tsx watch src/index.ts",
+    "start": "node dist/index.js"
+  },
+  "dependencies": {
+    "@codeboard/shared": "*",
+    "@codeboard/parser": "*",
+    "@codeboard/llm": "*",
+    "@codeboard/diagrams": "*",
+    "bullmq": "^5.34.0",
+    "ioredis": "^5.4.0",
+    "simple-git": "^3.27.0"
+  },
+  "devDependencies": {
+    "@types/node": "^20.0.0",
+    "tsx": "^4.19.0",
+    "typescript": "^5.7"
+  }
+}