feat: replace MaxMind ASN with iptoasn.com TSV backend

Drop GeoLite2-ASN.mmdb dependency (required license key) in favor of
iptoasn.com ip2asn-v4.tsv (no auth, public domain).  Bisect-based
lookup in pure stdlib, downloaded via SOCKS5 in update-data.sh.
Adds 30 test cases covering load, lookup, and command handler.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/update-data.sh

@@ -124,6 +124,26 @@ update_geolite2() {
     done
 }
 
+# -- iptoasn ASN database -----------------------------------------------------
+update_asn() {
+    local dest="$DATA_DIR/ip2asn-v4.tsv"
+    local url="https://iptoasn.com/data/ip2asn-v4.tsv.gz"
+    mkdir -p "$DATA_DIR"
+    dim "Downloading iptoasn database..."
+    if curl -sS -fL --max-time 60 -o "$dest.gz" "$url" ||
+       curl -sS -fL --socks5-hostname 127.0.0.1:1080 --max-time 60 \
+            -o "$dest.gz" "$url"; then
+        gunzip -f "$dest.gz"
+        local count
+        count=$(wc -l < "$dest")
+        info "iptoasn: $count ranges"
+    else
+        rm -f "$dest.gz"
+        err "Failed to download iptoasn database"
+        ((FAILURES++)) || true
+    fi
+}
+
 # -- Exploit-DB CSV -----------------------------------------------------------
 update_exploitdb() {
     local dest_dir="$DATA_DIR/exploitdb"
@@ -151,6 +171,7 @@ echo
 update_tor
 update_iprep
 update_oui
+update_asn
 update_exploitdb
 update_geolite2