Keep prefixes that do not parse out of the prefix tables (closes #114)

UpdatePrefixesBatch now skips a prefix that does not parse, so it never
becomes a row in prefixes_v4 or prefixes_v6 and never counts in the prefix
total in the stats. Before, the prefix handler stored no route for such a
prefix and logged it once per prefix and peer, but still passed it to
UpdatePrefixesBatch, which stored it.

Model: opus-5-5

internal/database/database.go

@@ -855,7 +855,7 @@ func insertPrefixesInTable(
 
 // UpdatePrefixesBatch stores, in a single transaction, the prefixes that are
 // not stored yet, each first seen at its time in prefixes: the IPv4 prefixes
-// first and then the IPv6 prefixes.
+// first and then the IPv6 prefixes. A prefix that does not parse is not stored.
 func (d *Database) UpdatePrefixesBatch(prefixes map[string]time.Time) error {
 	if len(prefixes) == 0 {
 		return nil
@@ -874,6 +874,11 @@ func (d *Database) UpdatePrefixesBatch(prefixes map[string]time.Time) error {
 	prefixesV6 := make(map[string]time.Time)
 
 	for prefix, timestamp := range prefixes {
+		_, err := netip.ParsePrefix(prefix)
+		if err != nil {
+			continue
+		}
+
 		if detectIPVersion(prefix) == ipVersionV4 {
 			prefixesV4[prefix] = timestamp
 		} else {