Back off WHOIS lookups more slowly and stop asking for personal data (closes #159)

A failed lookup now makes the fetcher's wait 1.5 times as long, up to
one minute instead of five. A success still halves it.

RIPE counts the person and role objects an answer holds against a daily
limit per IP address, and refuses an address for good that passes it
too often. RIPE, APNIC and AFRINIC are now asked with --no-personal,
which leaves those objects out but keeps the organisation object.

An answer with RIPE's access-denied or limit-reached error line is now
reported as a refusal holding that line, not as an answer with no
fields.

Model: opus-5-5

internal/routewatch/asnfetcher.go

@@ -21,10 +21,16 @@ const (
 	minInterval = 1 * time.Second
 
 	// maxInterval is the maximum interval after failures (backoff cap).
-	maxInterval = 5 * time.Minute
+	maxInterval = time.Minute
 
-	// backoffMultiplier is how much to multiply interval on failure.
-	backoffMultiplier = 2
+	// A failure multiplies the interval by backoffNumerator divided by
+	// backoffDenominator, 1.5, up to maxInterval.
+	backoffNumerator   = 3
+	backoffDenominator = 2
+
+	// A success divides the interval by successDivisor, down to
+	// minInterval.
+	successDivisor = 2
 
 	// whoisStaleThreshold is how old WHOIS data can be before refresh.
 	whoisStaleThreshold = 30 * 24 * time.Hour // 30 days
@@ -160,7 +166,7 @@ func (f *ASNFetcher) recordSuccess() {
 	f.consecutiveFails = 0
 
 	// Decrease interval by half, but not below minimum
-	newInterval := max(f.currentInterval/backoffMultiplier, minInterval)
+	newInterval := max(f.currentInterval/successDivisor, minInterval)
 
 	if newInterval != f.currentInterval {
 		f.logger.Debug("Decreased fetch interval",
@@ -184,8 +190,9 @@ func (f *ASNFetcher) recordFailure() {
 	f.intervalMu.Lock()
 	f.consecutiveFails++
 
-	// Exponential backoff: multiply by 2, capped at max
-	newInterval := min(f.currentInterval*backoffMultiplier, maxInterval)
+	// Exponential backoff: multiply by 1.5, capped at max
+	newInterval := min(
+		f.currentInterval*backoffNumerator/backoffDenominator, maxInterval)
 
 	if newInterval != f.currentInterval {
 		f.logger.Debug("Increased fetch interval due to failure",