feat: fase 3 — export PDF con reportlab + /export command

src/db/database.py

@@ -151,6 +151,14 @@ class ResearchDB:
         row = await cursor.fetchone()
         return dict(row) if row else None
 
+    async def get_latest_session(self, chat_id: int) -> Optional[dict]:
+        cursor = await self.db.execute(
+            "SELECT * FROM research_sessions WHERE telegram_chat_id = ? ORDER BY created_at DESC LIMIT 1",
+            (chat_id,)
+        )
+        row = await cursor.fetchone()
+        return dict(row) if row else None
+
     async def get_active_session(self, chat_id: int) -> Optional[dict]:
         cursor = await self.db.execute(
             """SELECT * FROM research_sessions