feat: caché de contenido de fuentes — reutiliza URLs scrapeadas en últimos 7 días

src/db/database.py

@@ -318,6 +318,19 @@ class ResearchDB:
         row = await cursor.fetchone()
         return row[0] if row else None
 
+    async def get_cached_content(self, url: str,
+                                  max_age_days: int = 7) -> Optional[str]:
+        threshold = time.time() - (max_age_days * 86400)
+        async with self.db.execute(
+            """SELECT sc.content FROM source_contents sc
+               JOIN sources s ON s.id = sc.source_id
+               WHERE s.url = ? AND sc.created_at > ?
+               ORDER BY sc.created_at DESC LIMIT 1""",
+            (url, threshold)
+        ) as cur:
+            row = await cur.fetchone()
+            return row[0] if row else None
+
     async def get_outputs(self, session_id: int) -> list[dict]:
         cursor = await self.db.execute(
             "SELECT * FROM outputs WHERE session_id = ? ORDER BY created_at DESC",