feat(tableau): export Excel via DuckDB (AST->SQL) (#41)

Rewrite download_data to read filterModel/columnState from the AG Grid
component and add export_dataframe (compiles filterModel to SQL via
filtermodel_to_ast/ast_to_sql, builds ORDER BY, excludes hidden columns,
queries DuckDB via query_marches). Replaces the old Polars filter_query
pipeline tied to the removed DataTable.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_main.py

@@ -99,7 +99,7 @@ def test_003_tableau_download(dash_duo: DashComposite):
     print(app.server.name)
 
     outputs = [
-        download_data(1, "", [], None),
+        download_data(1, None, None),
         download_acheteur_data(1, "/acheteurs/123", "2025", "ACHETEUR 1"),
         download_titulaire_data(1, "/titulaires/345", "2025", "TITULAIRE 1"),
     ]