feat: improve setup wizard UX, add cluster sync error handling, and conditional demo data seeding

Add SEED_DEMO_DATA environment variable to control demo data population, enhance setup wizard with welcome screen and theme toggle, add smooth animations for wizard transitions, improve dashboard endpoint to return structured objects for last_syncs and faulty_nodes instead of raw models, implement comprehensive error handling in cluster sync with failed status tracking and audit logging, fix Proxmox provider

backend/app/api/v1/router.py

@@ -148,14 +148,29 @@ def complete_setup(payload: SetupCompleteRequest, db: Session = Depends(get_db))
 
 @api_router.get("/dashboard")
 def dashboard(_: CurrentUser, db: Session = Depends(get_db)) -> dict:
+    last_syncs = db.scalars(select(Cluster).order_by(Cluster.updated_at.desc()).limit(5)).all()
+    faulty_nodes = db.scalars(select(Node).where(Node.status != "online")).all()
     return {
         "clusters": db.scalar(select(func.count()).select_from(Cluster)),
         "nodes": db.scalar(select(func.count()).select_from(Node)),
         "workloads": db.scalar(select(func.count()).select_from(Workload)),
         "networks": db.scalar(select(func.count()).select_from(Network)),
         "open_policy_violations": 1,
-        "last_syncs": db.scalars(select(Cluster).order_by(Cluster.updated_at.desc()).limit(5)).all(),
-        "faulty_nodes": db.scalars(select(Node).where(Node.status != "online")).all(),
+        "last_syncs": [
+            {
+                "id": cluster.id,
+                "name": cluster.name,
+                "provider": cluster.provider,
+                "status": cluster.last_sync_status,
+                "error": cluster.last_sync_error,
+                "at": cluster.last_sync_at.isoformat() if cluster.last_sync_at else None,
+            }
+            for cluster in last_syncs
+        ],
+        "faulty_nodes": [
+            {"id": node.id, "name": node.name, "status": node.status, "cluster_id": node.cluster_id}
+            for node in faulty_nodes
+        ],
         "top_talkers": [
             {"name": "finance-app-2", "bytes": 942000000},
             {"name": "core-services-1", "bytes": 512000000},
@@ -246,14 +261,31 @@ async def sync_cluster(cluster_id: str, user: CurrentUser, db: Session = Depends
     if not cluster:
         raise HTTPException(status_code=404, detail="Cluster not found")
     provider = get_provider(cluster.provider)
-    inventory = await provider.sync_inventory(
-        ProviderConnection(
-            api_url=cluster.api_url,
-            token=cluster.token_ref or "",
-            verify_tls=cluster.verify_tls,
-            read_only=cluster.mode == "read_only",
+    try:
+        inventory = await provider.sync_inventory(
+            ProviderConnection(
+                api_url=cluster.api_url,
+                token=cluster.token_ref or "",
+                verify_tls=cluster.verify_tls,
+                read_only=cluster.mode == "read_only",
+            )
         )
-    )
+    except Exception as exc:
+        cluster.last_sync_at = datetime.utcnow()
+        cluster.last_sync_status = "failed"
+        cluster.last_sync_error = str(exc)
+        db.add(Job(kind="proxmox.sync", status="failed", progress=100, logs=[f"Sync failed for {cluster.name}"], error=str(exc)))
+        db.commit()
+        write_audit(
+            db,
+            action="cluster.sync",
+            object_type="cluster",
+            object_id=cluster.id,
+            user_id=user.id,
+            result="failed",
+            error_text=str(exc),
+        )
+        raise HTTPException(status_code=502, detail=f"Provider sync failed: {exc}") from exc
     cluster.last_sync_at = datetime.utcnow()
     cluster.last_sync_status = "success"
     cluster.last_sync_error = None