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/web/src/components/mermaid-diagram.tsx

@@ -0,0 +1,82 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import mermaid from "mermaid";
+
+interface MermaidDiagramProps {
+  chart: string;
+}
+
+export function MermaidDiagram({ chart }: MermaidDiagramProps) {
+  const containerRef = useRef<HTMLDivElement>(null);
+  const [error, setError] = useState<string | null>(null);
+  const [isReady, setIsReady] = useState(false);
+
+  useEffect(() => {
+    mermaid.initialize({
+      startOnLoad: false,
+      theme: "dark",
+      securityLevel: "loose",
+      themeVariables: {
+        darkMode: true,
+        background: "#0a0a0f",
+        primaryColor: "#1e3a5f",
+        primaryTextColor: "#ffffff",
+        primaryBorderColor: "#3b82f6",
+        lineColor: "#6366f1",
+        secondaryColor: "#1f2937",
+        tertiaryColor: "#374151",
+        fontFamily: "ui-monospace, monospace",
+      },
+      flowchart: {
+        useMaxWidth: true,
+        htmlLabels: true,
+        curve: "basis",
+      },
+    });
+    setIsReady(true);
+  }, []);
+
+  useEffect(() => {
+    if (!isReady || !containerRef.current || !chart) return;
+
+    const renderChart = async () => {
+      try {
+        const id = `mermaid-${Math.random().toString(36).slice(2, 9)}`;
+        const { svg } = await mermaid.render(id, chart);
+        
+        if (containerRef.current) {
+          containerRef.current.innerHTML = svg;
+          setError(null);
+        }
+      } catch (err) {
+        setError(err instanceof Error ? err.message : "Failed to render diagram");
+      }
+    };
+
+    renderChart();
+  }, [chart, isReady]);
+
+  if (error) {
+    return (
+      <div className="p-4 rounded-lg bg-red-500/10 border border-red-500/20">
+        <p className="text-red-400 text-sm mb-2">Failed to render diagram</p>
+        <pre className="text-xs text-red-300/70 overflow-x-auto">{chart}</pre>
+      </div>
+    );
+  }
+
+  return (
+    <div 
+      ref={containerRef} 
+      className="mermaid-diagram overflow-x-auto"
+      style={{ minHeight: "100px" }}
+    >
+      {!isReady && (
+        <div className="flex items-center justify-center py-8">
+          <div className="w-6 h-6 border-2 border-blue-500/30 border-t-blue-500 rounded-full animate-spin" />
+        </div>
+      )}
+    </div>
+  );
+}