Add route age information to IP lookup API

- Add last_updated timestamp and age fields to ASInfo
- Include route's last_updated time from live_routes table
- Calculate and display age as human-readable duration
- Update both IPv4 and IPv6 queries to fetch timestamp
- Fix error handling to return 400 for invalid IPs

internal/database/models.go

@@ -70,8 +70,10 @@ type PrefixDistribution struct {
 
 // ASInfo represents AS information for an IP lookup
 type ASInfo struct {
-	ASN         int    `json:"asn"`
-	Handle      string `json:"handle"`
-	Description string `json:"description"`
-	Prefix      string `json:"prefix"`
+	ASN         int       `json:"asn"`
+	Handle      string    `json:"handle"`
+	Description string    `json:"description"`
+	Prefix      string    `json:"prefix"`
+	LastUpdated time.Time `json:"last_updated"`
+	Age         string    `json:"age"`
 }