feat: add dashboard metrics table

Author: ulemons

backend/src/database/migrations/U1764931554__create_dashboard_metrics_sink.sql

@@ -0,0 +1,11 @@
+CREATE TABLE public."dashboardMetricsSnapshot" (
+    id TEXT PRIMARY KEY DEFAULT 'snapshot',
+
+    "activitiesTotal" BIGINT,
+    "activitiesLast30Days" BIGINT,
+    "organizationsTotal" BIGINT,
+    "organizationsLast30Days" BIGINT,
+    "membersTotal" BIGINT,
+    "membersLast30Days" BIGINT,
+    "updatedAt" TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);