Rename the program to sww and its deciding daemon to discriminator

The program is now sww, built from cmd/sww, with two modes: sww rproxy and
sww discriminator. servewaf becomes discriminator everywhere it names that
daemon: the package (internal/discriminator), its types, functions, files, the
discriminator_line log field, and its docs and tests.

smallwebwaf is left only where sneak's directive allows it: the documents'
product name, the git.eeqj.de/sneak/smallwebwaf URLs, and the Go module path
sneak.berlin/go/smallwebwaf. Everywhere else a name containing it takes the sww
form: the package (internal/sww), metric names (sww_*), the X-Sww-* headers,
the /_sww/ admin endpoints, the OS user, and the state and rules directories.
The SWWAF_ environment variables take the SWW_ form.

No logic changes. make check passes.

Model: deepseek-v4-pro

internal/metrics/busiest.go

@@ -41,7 +41,7 @@ type busiest struct {
 // for the topN busiest countries.
 func newCountries(topN int) *busiest {
 	countries := newBusiest(topN, "country", "the client's country")
-	countries.refused = counterVec("smallwebwaf_country_list_refusals_total",
+	countries.refused = counterVec("sww_country_list_refusals_total",
 		"Requests the country lists refused, by the client's country.",
 		[]string{"country"})
 
@@ -61,11 +61,11 @@ func newBusiest(topN int, label, description string) *busiest {
 
 	return &busiest{
 		topN: topN,
-		requests: counterVec("smallwebwaf_"+label+"_requests_total",
+		requests: counterVec("sww_"+label+"_requests_total",
 			"Requests, by "+description+".", by),
-		requestBytes: counterVec("smallwebwaf_"+label+"_request_bytes_total",
+		requestBytes: counterVec("sww_"+label+"_request_bytes_total",
 			"Request body bytes, by "+description+".", by),
-		responseBytes: counterVec("smallwebwaf_"+label+"_response_bytes_total",
+		responseBytes: counterVec("sww_"+label+"_response_bytes_total",
 			"Response body bytes, by "+description+".", by),
 		seen: map[string]int64{},
 		top:  map[string]bool{},