fix: HIGH issues #12,#15,#16,#17,#21 — backend persistence for import/layers/blocks + owner filtering

backend/src/database/SqliteAdapter.ts

@@ -73,7 +73,10 @@ export class SqliteAdapter implements DatabaseInterface {
   }
 
   // ─── Projects ──────────────────────────────────────
-  listProjects(): DBProject[] {
+  listProjects(ownerId?: string): DBProject[] {
+    if (ownerId) {
+      return this.db.prepare('SELECT * FROM projects WHERE owner_id = ? ORDER BY updated_at DESC').all(ownerId) as DBProject[];
+    }
     return this.db.prepare('SELECT * FROM projects ORDER BY updated_at DESC').all() as DBProject[];
   }