feat(platform): harden telemetry pipeline and unify Semi UI workspaces

vehicle-data-platform/apps/api/internal/platform/schema_gate.go

@@ -0,0 +1,23 @@
+package platform
+
+import "sync"
+
+// schemaReadyGate serializes schema probes and caches only a successful result.
+// Request cancellation and transient database failures must remain retryable.
+type schemaReadyGate struct {
+	mu    sync.Mutex
+	ready bool
+}
+
+func (gate *schemaReadyGate) ensure(check func() error) error {
+	gate.mu.Lock()
+	defer gate.mu.Unlock()
+	if gate.ready {
+		return nil
+	}
+	if err := check(); err != nil {
+		return err
+	}
+	gate.ready = true
+	return nil
+}