Remove the CrowdSec decision feed (closes #315)

sneak ruled to remove it. Gone: the heuristic crowdsec, the ban cause
crowdsec and its earlier_bans count, the tag crowdsec, the settings
SWW_WAF_CROWDSEC_LAPI_URL and SWW_WAF_CROWDSEC_LAPI_KEY, the decision
list fetch and parse in internal/reputation, their tests, and every
mention in the README, SPEC.md and docs/. EVALUATION.md keeps its
comparison of tools.

The ban ledger's internal ban function loses its expires parameter,
which only CrowdSec bans used.

Model: opus-5-5

internal/state/state.go

@@ -104,7 +104,7 @@ var (
 	errVersion = errors.New("unknown version")
 	// errMissing is for an entry without a field it needs.
 	errMissing     = errors.New("has no")
-	errCause       = errors.New("is not limit, attack, admin or crowdsec")
+	errCause       = errors.New("is not limit, attack or admin")
 	errExpires     = errors.New("is not after its start")
 	errDestination = errors.New("is not webhook, slack or ntfy")
 	errScope       = errors.New(
@@ -967,7 +967,7 @@ func (e BanEntry) ban() bans.Ban {
 // each expires is read again as written. An expires not after the start
 // is refused too, since the netblock's next ban for a broken limit, three
 // times as long as this one, would then refuse nothing; and so is a cause
-// other than limit, attack, admin or crowdsec, most likely misspelt.
+// other than limit, attack or admin, most likely misspelt.
 func (f *bansFile) check(data []byte) error {
 	var written struct {
 		Bans []struct {
@@ -991,8 +991,7 @@ func (f *bansFile) check(data []byte) error {
 		case entry.Expires != nil && !entry.Expires.After(entry.Start):
 			return fmt.Errorf("entry %d's expires %w", i+1, errExpires)
 		case entry.Cause != "" && entry.Cause != bans.CauseLimit &&
-			entry.Cause != bans.CauseAttack && entry.Cause != bans.CauseAdmin &&
-			entry.Cause != bans.CauseCrowdSec:
+			entry.Cause != bans.CauseAttack && entry.Cause != bans.CauseAdmin:
 			return fmt.Errorf(
 				"entry %d's cause %q %w",
 				i+1,