feat(frontend): enhance API credentials system and build configuration

Add real API support in demo mode with credential checking, implement build-time version injection from package.json, and refactor update checking with 24-hour caching. Migrate landing page from Vue to Astro with comprehensive UI components including Hero, Features, Benefits, and Tech Stack sections. Update CI/CD workflow with expanded cache paths and security scanner version pinned.

backend/tools/favicon_cli.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/trackeep/backend/services"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: go run favicon_test.go <URL>")
+		fmt.Println("Example: go run favicon_test.go https://github.com")
+		os.Exit(1)
+	}
+
+	url := os.Args[1]
+	fmt.Printf("Testing favicon fetching for: %s\n\n", url)
+
+	// Test the enhanced favicon fetcher
+	fetcher := services.NewFaviconFetcher()
+
+	fmt.Println("=== Enhanced Favicon Fetcher ===")
+	start := time.Now()
+	favicon, err := fetcher.FetchFavicon(url)
+	duration := time.Since(start)
+
+	if err != nil {
+		fmt.Printf("❌ Error: %v\n", err)
+	} else if favicon == "" {
+		fmt.Printf("❌ No favicon found\n")
+	} else {
+		fmt.Printf("✅ Favicon found: %s (took %v)\n", favicon, duration)
+	}
+
+	fmt.Println("\n=== Multiple Favicon Candidates ===")
+	start = time.Now()
+	favicons := fetcher.FetchMultipleFavicons(url, 5)
+	duration = time.Since(start)
+
+	fmt.Printf("Found %d favicon candidates (took %v):\n", len(favicons), duration)
+	for i, f := range favicons {
+		fmt.Printf("  %d. %s\n", i+1, f)
+	}
+
+	fmt.Println("\n=== Original Metadata Service ===")
+	start = time.Now()
+	metadata, err := services.FetchWebsiteMetadata(url)
+	duration = time.Since(start)
+
+	if err != nil {
+		fmt.Printf("❌ Error: %v\n", err)
+	} else {
+		fmt.Printf("✅ Metadata fetched (took %v):\n", duration)
+		fmt.Printf("  Title: %s\n", metadata.Title)
+		fmt.Printf("  Description: %s\n", metadata.Description)
+		fmt.Printf("  Favicon: %s\n", metadata.Favicon)
+		fmt.Printf("  Site Name: %s\n", metadata.SiteName)
+	}
+
+	fmt.Println("\n=== Comparison ===")
+	if favicon != "" && metadata != nil && metadata.Favicon != "" {
+		if favicon == metadata.Favicon {
+			fmt.Println("✅ Both methods returned the same favicon")
+		} else {
+			fmt.Println("⚠️  Different favicons returned:")
+			fmt.Printf("  Enhanced: %s\n", favicon)
+			fmt.Printf("  Original: %s\n", metadata.Favicon)
+		}
+	} else if metadata == nil {
+		fmt.Println("⚠️  Original metadata service failed, enhanced method succeeded")
+	} else {
+		fmt.Println("⚠️  Could not compare favicon results")
+	}
+}