feat(ntfy): add the HTTP client, stream manager, and account discovery

Speak the ntfy JSON API directly: subscribe, publish, group topics that share a server and credentials, reconnect with backoff and a since cursor, and list account subscriptions, reservations, and ACL grants.

internal/ntfy/group_test.go

@@ -0,0 +1,22 @@
+package ntfy
+
+import (
+	"testing"
+
+	"lazyntfy/internal/config"
+)
+
+func TestGroupSubs(t *testing.T) {
+	subs := []config.Sub{
+		{Origin: "https://h", Name: "a", Auth: config.Auth{Token: "t"}},
+		{Origin: "https://h", Name: "b", Auth: config.Auth{Token: "t"}},
+		{Origin: "https://h", Name: "c", Auth: config.Auth{Token: "other"}},
+	}
+	groups := GroupSubs(subs)
+	if len(groups) != 2 || len(groups[0].Names) != 2 {
+		t.Fatalf("%+v", groups)
+	}
+	if groups[0].URL("all") != "https://h/a,b/json?since=all" {
+		t.Fatalf("url %s", groups[0].URL("all"))
+	}
+}