Enhance API and UI for incident management and live updates

- Added a new endpoint `/api/agg/incidents` to provide a normalized snapshot of incidents for fleet triage, including severity and recommended actions.
- Implemented live event streaming via `/api/live/events` for real-time updates on fleet status and incidents, enhancing observability.
- Updated the Web UI to include dedicated sections for incidents and live updates, improving user navigation and access to critical information.
- Enhanced API documentation to reflect new endpoints and their functionalities, ensuring clarity for developers and users.

docs/AGGREGATE_OPENAPI.yaml

@@ -106,6 +106,18 @@ paths:
             application/json:
               schema: { $ref: '#/components/schemas/AggEnvelopeFleetStatus' }
 
+  /api/agg/incidents:
+    get:
+      summary: Нормализованный snapshot инцидентов по флоту
+      parameters:
+        - $ref: '#/components/parameters/aliases'
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema: { $ref: '#/components/schemas/AggEnvelopeIncidents' }
+
 components:
   parameters:
     aliases:
@@ -173,6 +185,13 @@ components:
           properties:
             data: { $ref: '#/components/schemas/FleetStatusData' }
 
+    AggEnvelopeIncidents:
+      allOf:
+        - $ref: '#/components/schemas/AggSuccessBase'
+        - type: object
+          properties:
+            data: { $ref: '#/components/schemas/IncidentsData' }
+
     TrafficRow:
       type: object
       properties:
@@ -297,3 +316,43 @@ components:
         servers_total: { type: integer }
         servers_all_ok: { type: integer }
         servers_failed: { type: integer }
+
+    IncidentAction:
+      type: object
+      properties:
+        label: { type: string }
+        href: { type: string }
+
+    IncidentItem:
+      type: object
+      properties:
+        id: { type: string }
+        kind: { type: string }
+        severity:
+          type: string
+          enum: [info, warning, critical]
+        status:
+          type: string
+          enum: [firing]
+        title: { type: string }
+        summary: { type: string }
+        affected_aliases:
+          type: array
+          items: { type: string }
+        metric_name: { type: string }
+        metric_value: { type: number, format: float }
+        metric_threshold: { type: number, format: float }
+        actions:
+          type: array
+          items: { $ref: '#/components/schemas/IncidentAction' }
+
+    IncidentsData:
+      type: object
+      properties:
+        items:
+          type: array
+          items: { $ref: '#/components/schemas/IncidentItem' }
+        total: { type: integer }
+        critical_total: { type: integer }
+        warning_total: { type: integer }
+        info_total: { type: integer }