fix: improve setup error handling and health endpoint

- Add /api/v1/health endpoint for web app compatibility
- Add detailed error logging to setup handler
- Show actual error messages when config save fails
- Helps debug permission and filesystem issues

aggregator-server/cmd/server/main.go

@@ -23,10 +23,13 @@ func startWelcomeModeServer() {
 	// Add CORS middleware
 	router.Use(middleware.CORSMiddleware())
 
-	// Health check
+	// Health check (both endpoints for compatibility)
 	router.GET("/health", func(c *gin.Context) {
 		c.JSON(200, gin.H{"status": "waiting for configuration"})
 	})
+	router.GET("/api/v1/health", func(c *gin.Context) {
+		c.JSON(200, gin.H{"status": "waiting for configuration"})
+	})
 
 	// Welcome page with setup instructions
 	router.GET("/", setupHandler.ShowSetupPage)