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/lookuptest/lookuptest.go

@@ -17,7 +17,7 @@ import (
 const fileMode = 0o600
 
 // Network is what a lookup database holds about a netblock, of the fields
-// smallwebwaf reads: its AS number, such as AS64496, the AS's name, and
+// sww reads: its AS number, such as AS64496, the AS's name, and
 // its country, such as DE.
 type Network struct {
 	ASN     string