feat(alert): add Opsgenie provider

Support Opsgenie Alert API v2 with US/EU endpoint selection,
configurable priority (P1-P5), and GenieKey auth. TUI form
includes API key, priority picker, and EU instance toggle.

internal/alert/alert.go

@@ -110,6 +110,24 @@ func gotifyPayload(priority string) PayloadFunc {
 	}
 }
 
+func opsgeniePayload(priority string) PayloadFunc {
+	return func(title, message string) ([]byte, error) {
+		return json.Marshal(map[string]any{
+			"message":     limitMessage(title, 130),
+			"description": message,
+			"source":      "uptop",
+			"priority":    priority,
+		})
+	}
+}
+
+func limitMessage(s string, max int) string {
+	if len(s) <= max {
+		return s
+	}
+	return s[:max]
+}
+
 func GetProvider(cfg models.AlertConfig) Provider {
 	switch cfg.Type {
 	case "discord":
@@ -173,6 +191,20 @@ func GetProvider(cfg models.AlertConfig) Provider {
 			Payload: gotifyPayload(priority),
 			Headers: map[string]string{"X-Gotify-Key": cfg.Settings["token"]},
 		}
+	case "opsgenie":
+		priority := "P3"
+		if p, ok := cfg.Settings["priority"]; ok && p != "" {
+			priority = p
+		}
+		apiURL := "https://api.opsgenie.com/v2/alerts"
+		if eu, ok := cfg.Settings["eu"]; ok && eu == "true" {
+			apiURL = "https://api.eu.opsgenie.com/v2/alerts"
+		}
+		return &HTTPProvider{
+			URL:     apiURL,
+			Payload: opsgeniePayload(priority),
+			Headers: map[string]string{"Authorization": "GenieKey " + cfg.Settings["api_key"]},
+		}
 	default:
 		return nil
 	}

internal/alert/alert_test.go

@@ -196,8 +196,76 @@ func TestHTTPProviderGotify(t *testing.T) {
 	}
 }
 
+func TestHTTPProviderOpsgenie(t *testing.T) {
+	var received map[string]any
+	var authHeader string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		authHeader = r.Header.Get("Authorization")
+		json.NewDecoder(r.Body).Decode(&received)
+		w.WriteHeader(202)
+	}))
+	defer srv.Close()
+
+	p := GetProvider(models.AlertConfig{Type: "opsgenie", Settings: map[string]string{
+		"api_key":  "test-genie-key",
+		"priority": "P1",
+	}})
+	hp := p.(*HTTPProvider)
+	hp.URL = srv.URL
+
+	if err := p.Send(context.Background(), "Site Down", "mysite.com is unreachable"); err != nil {
+		t.Fatalf("Send: %v", err)
+	}
+	if authHeader != "GenieKey test-genie-key" {
+		t.Errorf("expected auth 'GenieKey test-genie-key', got '%s'", authHeader)
+	}
+	if received["message"] != "Site Down" {
+		t.Errorf("unexpected message: %v", received["message"])
+	}
+	if received["description"] != "mysite.com is unreachable" {
+		t.Errorf("unexpected description: %v", received["description"])
+	}
+	if received["source"] != "uptop" {
+		t.Errorf("expected source 'uptop', got '%v'", received["source"])
+	}
+	if received["priority"] != "P1" {
+		t.Errorf("expected priority 'P1', got '%v'", received["priority"])
+	}
+}
+
+func TestOpsgenieEUEndpoint(t *testing.T) {
+	p := GetProvider(models.AlertConfig{Type: "opsgenie", Settings: map[string]string{
+		"api_key": "key", "eu": "true",
+	}})
+	hp := p.(*HTTPProvider)
+	if hp.URL != "https://api.eu.opsgenie.com/v2/alerts" {
+		t.Errorf("expected EU URL, got '%s'", hp.URL)
+	}
+}
+
+func TestOpsgenieUSEndpoint(t *testing.T) {
+	p := GetProvider(models.AlertConfig{Type: "opsgenie", Settings: map[string]string{
+		"api_key": "key",
+	}})
+	hp := p.(*HTTPProvider)
+	if hp.URL != "https://api.opsgenie.com/v2/alerts" {
+		t.Errorf("expected US URL, got '%s'", hp.URL)
+	}
+}
+
+func TestLimitMessage(t *testing.T) {
+	short := "short"
+	if got := limitMessage(short, 130); got != short {
+		t.Errorf("expected '%s', got '%s'", short, got)
+	}
+	long := string(make([]byte, 200))
+	if got := limitMessage(long, 130); len(got) != 130 {
+		t.Errorf("expected length 130, got %d", len(got))
+	}
+}
+
 func TestGetProviderNewTypes(t *testing.T) {
-	for _, typ := range []string{"telegram", "pagerduty", "pushover", "gotify"} {
+	for _, typ := range []string{"telegram", "pagerduty", "pushover", "gotify", "opsgenie"} {
 		p := GetProvider(models.AlertConfig{Type: typ, Settings: map[string]string{
 			"token": "x", "chat_id": "1", "routing_key": "k", "user": "u", "url": "http://localhost",
 		}})