feat: v0.2.0 branding, healthz version, SSE dashboard live

Centralize APP_VERSION 0.2.0; /health and /healthz return version;
startup log line; UI title Security Alert Center v.0.2.0;
SSE /api/v1/stream/events for live dashboard counters.

frontend/src/views/DashboardView.vue

@@ -54,17 +54,20 @@
     </table>
     <div class="filters" style="margin-top: 1rem">
       <button type="button" class="secondary" @click="load">Обновить</button>
+      <span v-if="live" class="live-badge">live</span>
     </div>
   </template>
 </template>
 
 <script setup lang="ts">
-import { onMounted, ref } from "vue";
-import { apiFetch, type DashboardSummary } from "../api";
+import { onMounted, onUnmounted, ref } from "vue";
+import { apiFetch, getToken, type DashboardSummary } from "../api";
 
 const data = ref<DashboardSummary | null>(null);
 const loading = ref(false);
 const error = ref("");
+const live = ref(false);
+let eventSource: EventSource | null = null;
 
 function formatDt(iso: string) {
   return new Date(iso).toLocaleString("ru-RU");
@@ -82,5 +85,44 @@ async function load() {
   }
 }
 
-onMounted(() => load());
+function connectLive() {
+  const token = getToken();
+  if (!token) return;
+  eventSource?.close();
+  const url = `/api/v1/stream/events?token=${encodeURIComponent(token)}`;
+  eventSource = new EventSource(url);
+  eventSource.onopen = () => {
+    live.value = true;
+  };
+  eventSource.onmessage = (ev) => {
+    try {
+      const msg = JSON.parse(ev.data) as {
+        type?: string;
+        events_last_24h?: number;
+        problems_open?: number;
+      };
+      if (msg.type !== "dashboard" || !data.value) return;
+      if (typeof msg.events_last_24h === "number") {
+        data.value.events_last_24h = msg.events_last_24h;
+      }
+      if (typeof msg.problems_open === "number") {
+        data.value.problems_open = msg.problems_open;
+      }
+    } catch {
+      /* ignore malformed SSE */
+    }
+  };
+  eventSource.onerror = () => {
+    live.value = false;
+  };
+}
+
+onMounted(() => {
+  load().then(() => connectLive());
+});
+
+onUnmounted(() => {
+  eventSource?.close();
+  eventSource = null;
+});
 </script>