Add remote routing URL support (#6168)

* Add remote routing URL support

* Harden remote routing refresh

* fix(sub): harden remote routing fetch and accept Mihomo src rule flag

Remote routing bytes reach the YAML/JSON parsers from goroutines that run
outside Gin's recovery, so a parser panic on crafted input would take down
the whole panel. Contain it in fetch() (a panic now degrades to a failed
refresh that keeps the last-good value and releases the in-flight slot)
and start the refresh, cache-load and startup-warm goroutines through
common.GoRecover like the other background workers.

The route-graph validator only skipped a trailing no-resolve flag, so a
valid Mihomo rule like IP-CIDR,x,DIRECT,no-resolve,src was rejected as an
unknown target; skip both option flags.

Also deduplicate the HTTPS-source classification into
common.ParseRemoteRoutingURL so the save-time validator and the resolver
can never drift (internal/sub imports internal/web/service, so the copy
existed only to avoid the import cycle), move the test-only
mergeRemoteClashRulesYAML helper into the test file, and trim oversized
comment blocks.

---------

Co-authored-by: Duxxie <yelloduxx@users.noreply.github.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

internal/web/service/setting_remote_routing_test.go

@@ -0,0 +1,38 @@
+package service
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/web/entity"
+)
+
+func TestValidateRemoteRoutingURLSettings(t *testing.T) {
+	tests := []struct {
+		name      string
+		value     string
+		want      string
+		wantError string
+	}{
+		{name: "valid HTTPS", value: " https://example.com/rules#fragment ", want: "https://example.com/rules"},
+		{name: "credentials", value: "https://user:pass@example.com/rules", wantError: "must not contain URL credentials"},
+		{name: "missing host", value: "https:///rules", wantError: "absolute HTTPS URL"},
+		{name: "legacy HTTP stays inline", value: "http://example.com/rules", want: "http://example.com/rules"},
+		{name: "multiline Clash stays inline", value: "https://example.com/rules\nMATCH,PROXY", want: "https://example.com/rules\nMATCH,PROXY"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			settings := &entity.AllSetting{SubRoutingRules: tt.value}
+			err := validateSettingsURLs(settings)
+			if tt.wantError != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.wantError) {
+					t.Fatalf("err=%v, want %q", err, tt.wantError)
+				}
+				return
+			}
+			if err != nil || settings.SubRoutingRules != tt.want {
+				t.Fatalf("value=%q err=%v", settings.SubRoutingRules, err)
+			}
+		})
+	}
+}