feat: embed React frontend in Go binary with SPA fallback

cmd/server/main.go

@@ -3,7 +3,9 @@ package main
 
 import (
 	"context"
+	"embed"
 	"fmt"
+	"io/fs"
 	"log"
 	"net/http"
 	"os"
@@ -22,6 +24,9 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+//go:embed all:src/dist
+var frontendFS embed.FS
+
 // Config holds the application configuration.
 type Config struct {
 	DBPath       string        `yaml:"db_path"`
@@ -84,6 +89,9 @@ func main() {
 	// API routes (auth required if API key is configured)
 	r.Mount("/api/v1", auth.Middleware(cfg.APIKey)(apiRouter(sseHub, sqlDB)))
 
+	// Serve embedded React frontend with SPA fallback
+	r.Mount("/", frontendHandler())
+
 	// Create server
 	httpServer := &http.Server{
 		Addr:         ":" + cfg.Port,
@@ -158,4 +166,37 @@ func loadConfig(path string) (*Config, error) {
 	}
 
 	return &cfg, nil
+}
+
+// frontendHandler returns an http.Handler that serves the embedded React
+// frontend from src/dist/ with SPA-style fallback: any path that doesn't
+// match a static file serves index.html for client-side routing.
+//
+// The frontend is embedded via //go:embed all:src/dist at build time.
+// If src/dist/ is empty or missing at build time, the embedded fallback
+// index.html (committed to the repo) is served instead, showing a
+// "run npm run build" message.
+func frontendHandler() http.Handler {
+	distFS, err := fs.Sub(frontendFS, "src/dist")
+	if err != nil {
+		// Shouldn't happen if embed worked, but be defensive.
+		panic("embedded frontend filesystem not found: " + err.Error())
+	}
+
+	fileServer := http.FileServer(http.FS(distFS))
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Try to serve the requested file.
+		f, err := distFS.Open(r.URL.Path[1:]) // strip leading "/"
+		if err != nil {
+			// File not found — serve index.html for SPA routing.
+			r.URL.Path = "/"
+			fileServer.ServeHTTP(w, r)
+			return
+		}
+		f.Close()
+
+		// File exists, serve it.
+		fileServer.ServeHTTP(w, r)
+	})
 }