Rename the program to sww and its deciding daemon to discriminator (closes #218)

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/config/rproxy_test.go

@@ -24,7 +24,7 @@ const (
 	rproxyMaxResponse = "SWRP_MAX_RESPONSE_SIZE"
 	rproxyRequestTime = "SWRP_MAX_REQUEST_TIME_MS"
 	rproxyAnswerTime  = "SWRP_MAX_RESPONSE_TIME_MS"
-	backendURL        = "http://servewaf:8080"
+	backendURL        = "http://discriminator:8080"
 	rproxyDefaultAddr = ":8080"
 	rproxyDefaultApp  = "http://127.0.0.1:8081"
 	notASize          = "a lot"
@@ -114,8 +114,8 @@ func TestRProxyInvalidSettingsAreRefused(t *testing.T) {
 		name, value string
 	}{
 		{wafBackend, ""},
-		{wafBackend, "servewaf:8080"},
-		{wafBackend, "http://servewaf:8080/path"},
+		{wafBackend, "discriminator:8080"},
+		{wafBackend, "http://discriminator:8080/path"},
 		{rproxyTimeout, "0"},
 		{rproxyTimeout, "-1"},
 		{rproxyTimeout, off},