fix(instagram): scope saved sessions to the configured account

bot/modules/instagram/auth.py

@@ -69,18 +69,32 @@ class SessionPool:
         self._totp_secret = totp_secret
         self._live.extend(Session(s) for s in self._load() if s not in sids)
 
-    @staticmethod
-    def _load() -> list[str]:
+    def _load(self) -> list[str]:
         try:
             with open(STORE, "rb") as f:
-                return orjson.loads(f.read())
+                saved = orjson.loads(f.read())
         except Exception:
             return []
 
+        # Sessions are tied to the account that minted them. Swapping
+        # IG_USERNAME must not silently keep serving from the old one.
+        if isinstance(saved, dict):
+            if saved.get("user") != self._username:
+                return []
+            return saved.get("sids") or []
+        return saved if isinstance(saved, list) and not self._username else []
+
     def _save(self) -> None:
         try:
             with open(STORE, "wb") as f:
-                f.write(orjson.dumps([s.sid for s in self._live]))
+                f.write(
+                    orjson.dumps(
+                        {
+                            "user": self._username,
+                            "sids": [s.sid for s in self._live],
+                        }
+                    )
+                )
         except Exception:
             pass