Fix shadow-table scan link and add SQL pushdown coverage

[adsharma]

Stacked on the DuckLake pushdown work (first commit below belongs to that series; this PR's change is the last commit).

Fix: moved-from pointer disabled all pushdown over attached node tables

In DuckDBCatalog::createForeignTable, the attached entry pointer was read back from the unique_ptr after moving it into the catalog, so it was always null. The shadow node entry's referencedEntry was therefore null, getBoundScanInfo() returned null, and the planner emitted plain SCAN_NODE_TABLE instead of a pushdown-capable TABLE_FUNCTION_CALL — silently disabling the entire foreign join pushdown (and failing MATCH traversal) for DuckDB-attached node tables. Fixed by capturing the raw pointer before the move (the catalog takes ownership, so it stays valid).

Tests

Adds the pushdown_graph.db fixture (person/city nodes, knows/likes/lives-in rels with FKs) and sql_pushdown.test covering:

• 1-hop baseline with ORDER BY
• 2-hop with node filter (a.age > 30)
• 2-hop with edge filters (r1.since, r2.score)
• 2-hop across mixed node labels (person -> city)
• aggregation + ORDER BY (count(*) + ORDER BY cnt DESC)
• recursive CTE (-[e:rel_knows*1..3]->)
• recursive with inline edge filter (-[e:rel_knows*1..2 {since: 2020}]->)

Every MATCH here runs over rel_* tables, whose local traversal errors out, so each passing result proves the pattern pushed to SQL. Requires the companion engine change (ladybug PR) for the multi-hop/agg/recursive cases; the 1-hop cases pass with this fix alone.

CI: run the rest on CI (make extension-test needs the RelWithDebInfo extension tree).