feat: support rss datasource (#13721)

### What problem does this PR solve?

Supporting public RSS/Atom feed URLs as data sources for RagFlow.

link https://github.com/infiniflow/ragflow/issues/12313

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/svr/sync_data_source.py

@@ -43,6 +43,7 @@ from common import settings
 from common.config_utils import show_configs
 from common.data_source import (
     BlobStorageConnector,
+    RSSConnector,
     NotionConnector,
     DiscordConnector,
     GoogleDriveConnector,
@@ -243,6 +244,26 @@ class GOOGLE_CLOUD_STORAGE(_BlobLikeBase):
     DEFAULT_BUCKET_TYPE: str = "google_cloud_storage"
 
 
+class RSS(SyncBase):
+    SOURCE_NAME: str = FileSource.RSS
+
+    async def _generate(self, task: dict):
+        self.connector = RSSConnector(
+            feed_url=self.conf["feed_url"],
+            batch_size=self.conf.get("batch_size", INDEX_BATCH_SIZE),
+        )
+        self.connector.load_credentials(self.conf.get("credentials", {}))
+        self.connector.validate_connector_settings()
+
+        if task["reindex"] == "1" or not task["poll_range_start"]:
+            return self.connector.load_from_state()
+
+        return self.connector.poll_source(
+            task["poll_range_start"].timestamp(),
+            datetime.now(timezone.utc).timestamp(),
+        )
+
+
 class Confluence(SyncBase):
     SOURCE_NAME: str = FileSource.CONFLUENCE
 
@@ -1347,6 +1368,7 @@ class PostgreSQL(SyncBase):
 
 
 func_factory = {
+    FileSource.RSS: RSS,
     FileSource.S3: S3,
     FileSource.R2: R2,
     FileSource.OCI_STORAGE: OCI_STORAGE,