refactor: rename memory_entity→knowledge_node, knowledge graph edge→knowledge_edge

Resolves table name collision between:
- memory_edge (provenance DAG: child_sha/parent_sha) — KEPT
- knowledge_edge (knowledge graph: source_id/target_id) — NEW NAME

Changes:
- memory_entity → knowledge_node (all .rs + migrations 003-009)
- knowledge graph memory_edge → knowledge_edge
- memory_entity_version → knowledge_node_version
- memory_edge_version → knowledge_edge_version
- Added knowledge_node + knowledge_edge to init_schema()
- Converted versioning.rs from sqlx::query_as! to runtime queries
  (avoids stale sqlx offline cache dependency)
- Fixed UUID cast: $1::UUID for String→UUID column binds
- Fixed column names: source_entity_id→source_id, target_entity_id→target_id

Production DB: knowledge_node + knowledge_edge tables created,
memory_entity VIEW points to knowledge_node for backward compat.

crates/mem-cli/src/query/faceted_search.rs

@@ -108,7 +108,7 @@ impl FacetedSearch {
         // Get entity types
         let entity_types = sqlx::query_as::<_, (String, i64)>(
             "SELECT entity_type, COUNT(*) as cnt 
-             FROM memory_entity 
+             FROM knowledge_node 
              WHERE deleted_at IS NULL 
              GROUP BY entity_type 
              ORDER BY cnt DESC 
@@ -128,7 +128,7 @@ impl FacetedSearch {
 
         // Get total count
         let total_count: (i64,) = sqlx::query_as(
-            "SELECT COUNT(*) FROM memory_entity WHERE deleted_at IS NULL"
+            "SELECT COUNT(*) FROM knowledge_node WHERE deleted_at IS NULL"
         )
             .fetch_one(&self.pool)
             .await
@@ -212,7 +212,7 @@ impl FacetedSearch {
         // Get relation types
         let relation_types = sqlx::query_as::<_, (String, i64)>(
             "SELECT relation_type, COUNT(*) as cnt 
-             FROM memory_edge 
+             FROM knowledge_edge 
              WHERE fact_invalid_at IS NULL AND deleted_at IS NULL 
              GROUP BY relation_type 
              ORDER BY cnt DESC 
@@ -232,7 +232,7 @@ impl FacetedSearch {
 
         // Get total count
         let total_count: (i64,) = sqlx::query_as(
-            "SELECT COUNT(*) FROM memory_edge WHERE fact_invalid_at IS NULL AND deleted_at IS NULL"
+            "SELECT COUNT(*) FROM knowledge_edge WHERE fact_invalid_at IS NULL AND deleted_at IS NULL"
         )
             .fetch_one(&self.pool)
             .await