feat: add Matrix chat notification support (#211)

Implements native Matrix notification channel support, allowing users
to receive service alerts in any Matrix room via the Client-Server API.

Changes:
- server/service-operation/notification/matrix.go: new Matrix service
  implementing the NotificationService interface (PUT /_matrix/client/v3/...)
- server/service-operation/notification/types.go: add MatrixHomeserver,
  MatrixRoomID, MatrixAccessToken fields to AlertConfiguration
- server/service-operation/notification/manager.go: register MatrixService
- server/pb_migrations/1772200000_updated_alert_configurations_matrix.js:
  PocketBase migration adding matrix fields and notification_type value
- application: Matrix option in channel dialog with homeserver/room/token
  fields, tab filter, list display, type definitions and translations (en, km)
- application/public/upload/notification/matrix.png: Matrix channel icon

application/src/components/settings/notification-settings/NotificationSettings.tsx

@@ -154,6 +154,7 @@ const NotificationSettings = () => {
             <TabsTrigger value="google_chat">{t("googleChat")}</TabsTrigger>
             <TabsTrigger value="email">{t("email")}</TabsTrigger>
             <TabsTrigger value="webhook">{t("webhook")}</TabsTrigger>
+            <TabsTrigger value="matrix">{t("matrix")}</TabsTrigger>
           </TabsList>
           
           <TabsContent value={currentTab} className="mt-0">