Add config validation and dashboard

Add YAML config loading with validation, env overrides for secrets, and
a web dashboard exposing health, stats, and recent events.

uptime_kuma_test.v

@@ -0,0 +1,41 @@
+module main
+
+import sources
+
+fn test_transform_uptime_kuma_down() {
+	raw := '{"monitor":{"name":"Gitea"},"heartbeat":{"status":"down","msg":"503","time":"14:32"}}'
+	src := sources.UptimeKumaSource{
+		name:         'Critical'
+		webhook_path: '/webhooks/kuma'
+		topic:        'alerts'
+		state_map:    {
+			'down': sources.UptimeKumaState{
+				priority: 5
+				tags:     ['rotating_light']
+			}
+		}
+	}
+	event := sources.transform_uptime_kuma(raw, src) or { panic(err) }
+	assert event.source == 'uptime_kuma'
+	assert event.priority == 5
+	assert event.message.contains('Gitea')
+	assert event.message.contains('DOWN')
+}
+
+fn test_transform_uptime_kuma_up() {
+	raw := '{"monitor":{"name":"Gitea"},"heartbeat":{"status":"up"}}'
+	src := sources.UptimeKumaSource{
+		name:         'Critical'
+		webhook_path: '/webhooks/kuma'
+		topic:        'alerts'
+		state_map:    {
+			'up': sources.UptimeKumaState{
+				priority: 1
+				tags:     ['white_check_mark']
+			}
+		}
+	}
+	event := sources.transform_uptime_kuma(raw, src) or { panic(err) }
+	assert event.priority == 1
+	assert event.message.contains('UP')
+}