Add IPv4 range optimization for IP to AS lookups

- Add v4_ip_start and v4_ip_end columns to live_routes table
- Calculate IPv4 CIDR ranges as 32-bit integers for fast lookups
- Update PrefixHandler to populate IPv4 range fields
- Add GetASInfoForIP method with optimized IPv4 queries
- Add comprehensive tests for IP conversion functions

internal/database/models.go

@@ -57,6 +57,9 @@ type LiveRoute struct {
 	ASPath      []int     `json:"as_path"`
 	NextHop     string    `json:"next_hop"`
 	LastUpdated time.Time `json:"last_updated"`
+	// IPv4 range fields for fast lookups (nil for IPv6)
+	V4IPStart *uint32 `json:"v4_ip_start,omitempty"`
+	V4IPEnd   *uint32 `json:"v4_ip_end,omitempty"`
 }
 
 // PrefixDistribution represents the distribution of prefixes by mask length
@@ -64,3 +67,11 @@ type PrefixDistribution struct {
 	MaskLength int `json:"mask_length"`
 	Count      int `json:"count"`
 }
+
+// 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"`
+}