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/http_server.rs

@@ -383,11 +383,11 @@ pub async fn start_server(port: u16, api_key: String, database_url: &str) -> Res
             loop {
                 interval.tick().await;
                 // O5: Table row counts
-                if let Ok(row) = sqlx::query_as::<_, (i64,)>("SELECT COUNT(*) FROM memory_entity")
+                if let Ok(row) = sqlx::query_as::<_, (i64,)>("SELECT COUNT(*) FROM knowledge_node")
                     .fetch_one(&stats_pool).await {
                     crate::metrics::DB_TABLE_ENTITY_ROWS.set(row.0 as u64);
                 }
-                if let Ok(row) = sqlx::query_as::<_, (i64,)>("SELECT COUNT(*) FROM memory_edge")
+                if let Ok(row) = sqlx::query_as::<_, (i64,)>("SELECT COUNT(*) FROM knowledge_edge")
                     .fetch_one(&stats_pool).await {
                     crate::metrics::DB_TABLE_EDGE_ROWS.set(row.0 as u64);
                 }
@@ -1454,7 +1454,7 @@ async fn query_temporal_graph(
 ) -> anyhow::Result<serde_json::Value> {
     // Step 1: Find entities (order by name for deterministic results)
     let entities_rows: Vec<(String, String, String)> = sqlx::query_as(
-        "SELECT id, name, entity_type FROM memory_entity WHERE project_id = $1 LIMIT $2"
+        "SELECT id::TEXT, name, entity_type FROM knowledge_node WHERE project_id = $1 LIMIT $2"
     )
     .bind(&params.project)
     .bind(params.limit as i32)
@@ -1470,7 +1470,7 @@ async fn query_temporal_graph(
     for (entity_id, _name, _type_str) in &entities_rows {
         let entity_edges: Vec<(String, String, String, String, f32, Option<chrono::DateTime<chrono::Utc>>, Option<chrono::DateTime<chrono::Utc>>)> = 
             sqlx::query_as(
-                "SELECT id, target_entity_id, relation_type, fact, confidence, t_valid, t_invalid FROM memory_edge WHERE project_id = $1 AND source_entity_id = $2"
+                "SELECT id::TEXT, target_id::TEXT, relation_type, fact, confidence, t_valid, t_invalid FROM knowledge_edge WHERE project_id = $1 AND source_id = $2::UUID"
             )
             .bind(&params.project)
             .bind(entity_id)