refactor(planner): remove DataFusion from query planning path

Remove DataFusion SessionContext, UDF registration, catalog provider,
and all DataFusion-dependent helpers from QueryContext. Planning now
goes exclusively through nodedb-sql.

Deleted (~1700 lines):
- catalog.rs (DataFusion SchemaProvider)
- expr_convert.rs, sql_expr_convert.rs (DataFusion Expr converters)
- hints.rs (query hint extraction)
- stream_table/ (DataFusion table provider for change streams)

Simplified:
- context.rs: removed session field, UDF registration, inliner
- prepared/parser.rs: replaced DataFusion type inference with
  sqlparser + nodedb-sql catalog lookup
- routing.rs: removed dead temp table register/deregister
- eval.rs: uses standalone DataFusion session (not QueryContext)

DataFusion remains only for:
- Procedural executor scalar expression evaluation (eval.rs)
- Function body validation at CREATE FUNCTION (validate.rs)
- UDF trait implementations (needed by above two)

Author: farhan-syah

nodedb/src/control/planner/catalog.rs

@@ -1,14 +1,9 @@
 pub(crate) mod auto_tier;
-pub mod catalog;
 pub mod catalog_adapter;
 pub mod context;
-pub mod expr_convert;
-pub mod hints;
 pub mod physical;
 pub mod procedural;
 pub mod rls_injection;
-pub mod sql_expr_convert;
 pub mod sql_plan_convert;
-pub mod stream_table;
 pub mod udf;
 pub mod wasm;

nodedb/src/control/planner/context.rs

@@ -128,16 +128,16 @@ pub async fn evaluate_to_value(
 /// Execute a SQL expression via DataFusion and return the result batches.
 ///
 /// Wraps the expression in `SELECT (<expr>) as __result` and collects.
+/// Uses a standalone DataFusion session (not QueryContext) for scalar evaluation.
 pub async fn eval_sql_expr(
-    state: &SharedState,
-    tenant_id: TenantId,
+    _state: &SharedState,
+    _tenant_id: TenantId,
     expr: &str,
     context: &str,
 ) -> crate::Result<Vec<datafusion::arrow::record_batch::RecordBatch>> {
-    let ctx = crate::control::planner::context::QueryContext::for_state(state, tenant_id.as_u32());
+    let session = datafusion::execution::context::SessionContext::new();
     let select_sql = format!("SELECT ({expr}) as __result");
-    let df = ctx
-        .session()
+    let df = session
         .sql(&select_sql)
         .await
         .map_err(|e| crate::Error::PlanError {