Read every setting through viper and rename the settings (closes #211)

Every setting of discriminator and rproxy is read through viper, in place
of the os.LookupEnv function Main passed down. NewViper turns AutomaticEnv
and AllowEmptyEnv on, so a setting that is set but empty reads as set. A
setting may also be given as a file, the _FILE form, which rproxy's
settings now have too; rproxy still writes nothing to disk.

The settings are renamed. Discriminator's take the prefix SWW_WAF_,
rproxy's take SWW_RPROXY_, and the shared SWW_COMMAND keeps SWW_. The Core
Rule Set's settings take SWW_WAF_CORE_RULE_SET_ rather than SWW_WAF_WAF_.
Every place a name appeared changed: the code, the viper keys, tests,
documents, examples, the README's settings table and the image files.

Model: deepseek-v4-pro

internal/discriminator/bans.go

@@ -12,7 +12,7 @@ import (
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
 )
 
-// banResponse is a refusal answered with SWW_BAN_RESPONSE, and logged
+// banResponse is a refusal answered with SWW_WAF_BAN_RESPONSE, and logged
 // with action.
 func (rq *request) banResponse(action string) *refusal {
 	return &refusal{status: rq.h.config.BanResponse, action: action}
@@ -85,8 +85,8 @@ func (rq *request) countBytes() {
 // countRefusal counts the request for the error burst once it has been
 // answered, if discriminator refused it after a rule file match, a trap path or a
 // Core Rule Set match, and in observe mode if enforce mode would have: more than
-// SWW_ERROR_BURST_THRESHOLD such refusals of the client within a minute
-// break a limit. A client in SWW_ALLOW_NETS, which the checks skip, is
+// SWW_WAF_ERROR_BURST_THRESHOLD such refusals of the client within a minute
+// break a limit. A client in SWW_WAF_ALLOW_NETS, which the checks skip, is
 // not counted, and nothing is while the threshold is off.
 func (rq *request) countRefusal() {
 	cfg := rq.h.config
@@ -121,7 +121,7 @@ func (rq *request) countRefusal() {
 
 // countedBytes returns the request's bytes, once it has ended, as the
 // byte limits and the anomaly thresholds count them: the response's body
-// bytes, the request's, or both, as SWW_BYTES_COUNT says.
+// bytes, the request's, or both, as SWW_WAF_BYTES_COUNT says.
 func (rq *request) countedBytes() int64 {
 	response, request := rq.out.bytes, rq.requestBytes
 
@@ -138,7 +138,7 @@ func (rq *request) countedBytes() int64 {
 // banForLimit bans the client's netblock at now for a broken limit, the
 // one hit names, notes the offence for the log line and counts the hit in
 // the metrics. status is what the client was sent, or is sent:
-// SWW_BAN_RESPONSE for a request over a rate limit, what the report says for
+// SWW_WAF_BAN_RESPONSE for a request over a rate limit, what the report says for
 // one whose bytes broke a byte limit, the refusal for one that broke the
 // error burst. The ban's notes give the client's limit percentage for a
 // rate limit or a byte limit; the error burst is not lowered. The ban sets
@@ -277,7 +277,7 @@ func (rq *request) banForCrowdSec(now time.Time, decision reputation.Decision) {
 // wouldAlertBan reports whether the alert for a ban on netblock for cause
 // made at now would be sent. In observe mode the ban the request would
 // have made is worked out only then, at most once per
-// SWW_ALERT_COOLDOWN and never with no webhook set: its notes count the
+// SWW_WAF_ALERT_COOLDOWN and never with no webhook set: its notes count the
 // netblock's requests, which can mean going through every client.
 func (rq *request) wouldAlertBan(
 	netblock netip.Prefix, now time.Time, cause string,
@@ -343,7 +343,7 @@ func (rq *request) netblockRequests(netblock netip.Prefix) int64 {
 }
 
 // netblock is the netblock a ban on client covers: its IPv4 address,
-// widened to SWW_BAN_SCOPE_V4_PREFIX, or the IPv6 group clientGroup
+// widened to SWW_WAF_BAN_SCOPE_V4_PREFIX, or the IPv6 group clientGroup
 // counts it in.
 func (h *handler) netblock(client netip.Addr) netip.Prefix {
 	addr := client.Unmap()