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/lookup/file.go

@@ -24,7 +24,7 @@ const quietTime = 2 * time.Second
 // FileParams are what OpenFile needs.
 type FileParams struct {
 	// Path is the lookup database, the IPinfo Lite file in its .mmdb form
-	// (SWWAF_LOOKUP_DB_PATH).
+	// (SWW_LOOKUP_DB_PATH).
 	Path string
 	// Now tells the time, normally time.Now.
 	Now func() time.Time
@@ -51,7 +51,7 @@ type File struct {
 }
 
 // record is what the lookup database holds about a network, of the fields
-// smallwebwaf reads.
+// sww reads.
 type record struct {
 	ASN         string `maxminddb:"asn"`
 	ASName      string `maxminddb:"as_name"`
@@ -221,12 +221,12 @@ func (f *File) use(reader *maxminddb.Reader) {
 func read(path string) (*maxminddb.Reader, error) {
 	data, err := os.ReadFile(path) //nolint:gosec // the file the admin names
 	if err != nil {
-		return nil, fmt.Errorf("SWWAF_LOOKUP_DB_PATH cannot be read: %w", err)
+		return nil, fmt.Errorf("SWW_LOOKUP_DB_PATH cannot be read: %w", err)
 	}
 
 	reader, err := maxminddb.OpenBytes(data)
 	if err != nil {
-		return nil, fmt.Errorf("SWWAF_LOOKUP_DB_PATH %s is not a .mmdb file: %w", path, err)
+		return nil, fmt.Errorf("SWW_LOOKUP_DB_PATH %s is not a .mmdb file: %w", path, err)
 	}
 
 	return reader, nil