fix: URL-decode channel_id path params, strip @ prefix for state lookup

webui_server.py

@@ -1830,7 +1830,7 @@ class TelegramScraperRequestHandler(BaseHTTPRequestHandler):
             return self.send_json(list_channels_snapshot())
         if path.startswith("/api/channels/") and path.endswith("/messages"):
             parts = path.split("/")
-            channel_id = parts[3]
+            channel_id = urllib.parse.unquote(parts[3]).lstrip("@")
             limit = max(1, min(int(query.get("limit", ["120"])[0]), 300))
             before = query.get("before")
             before_message_id = int(before[0]) if before else None
@@ -1919,7 +1919,7 @@ class TelegramScraperRequestHandler(BaseHTTPRequestHandler):
         if sub == ["channels"]:
             return self._handle_get_account_channels(account_id)
         if len(sub) >= 3 and sub[0] == "channels" and sub[-1] == "messages":
-            channel_id = sub[1]
+            channel_id = urllib.parse.unquote(sub[1]).lstrip("@")
             return self._handle_get_account_channel_messages(account_id, channel_id, query)
         if sub == ["continuous"]:
             return self.send_json(
@@ -2409,6 +2409,7 @@ class TelegramScraperRequestHandler(BaseHTTPRequestHandler):
         return self.send_json(payload)
 
     def _handle_account_channel_add(self, account_id: str, channel_id: str, name: Optional[str]) -> None:
+        channel_id = channel_id.lstrip("@")
         if not channel_id:
             return self.send_error_json(HTTPStatus.BAD_REQUEST, "channel_id is required")
         store = get_account_store(DATA_DIR, account_id)