feat: add Vite configuration with aliases and proxy

Add path aliases (@/* -> src/*) and development proxy
configuration for API routing.

vite.config.ts

@@ -20,6 +20,43 @@ export default defineConfig({
     optimizeDeps: {
         entries: ["src/**/*.{ts,tsx}"],
     },
+    build: {
+        rollupOptions: {
+            output: {
+                manualChunks(id: string) {
+                    if (id.includes("node_modules")) {
+                        // React + deps that import React — keep together to avoid circular deps
+                        if (id.includes("react-dom") || id.includes("react-router-dom") || id.includes("scheduler") || id.includes("@tanstack/react-query")) {
+                            return "vendor-react";
+                        }
+                        if (id.includes("react-markdown") || id.includes("remark-gfm") || id.includes("rehype-raw") || id.includes("rehype-sanitize")) {
+                            return "vendor-markdown";
+                        }
+                        if (id.includes("lucide-react")) {
+                            return "vendor-lucide";
+                        }
+                        if (id.includes("motion")) {
+                            return "vendor-motion";
+                        }
+                        if (id.includes("recharts")) {
+                            return "vendor-recharts";
+                        }
+                        // Streamdown + diagram deps — keep together to avoid circular deps
+                        if (id.includes("streamdown") || id.includes("@streamdown") || id.includes("cytoscape") || id.includes("d3-") || id.includes("dagre")) {
+                            return "vendor-streamdown";
+                        }
+                        if (id.includes("@tanstack/react-table")) {
+                            return "vendor-table";
+                        }
+                        if (id.includes("radix-ui")) {
+                            return "vendor-radix";
+                        }
+                    }
+                },
+            },
+        },
+        chunkSizeWarningLimit: 400,
+    },
     resolve: {
         alias: {
             "@": path.resolve(__dirname, "./src"),