feat: add permanent public URL support for remote storage (OSS/S3)

api/app/core/storage/base.py

@@ -121,3 +121,18 @@ class StorageBackend(ABC):
             URL for accessing the file.
         """
         pass
+
+    async def get_permanent_url(self, file_key: str) -> Optional[str]:
+        """
+        Get a permanent public URL for the file (no expiration).
+
+        Returns None by default; remote storage backends should override this
+        if the bucket is configured for public read access.
+
+        Args:
+            file_key: Unique identifier for the file in the storage system.
+
+        Returns:
+            A permanent public URL, or None if not supported.
+        """
+        return None

api/app/core/storage/oss.py

@@ -261,3 +261,13 @@ class OSSStorage(StorageBackend):
             logger.error(f"Failed to generate presigned URL for {file_key}: {e}")
             # Return a basic URL format as fallback
             return f"https://{self.bucket_name}.{self.endpoint.replace('https://', '').replace('http://', '')}/{file_key}"
+
+    async def get_permanent_url(self, file_key: str) -> str:
+        """
+        Get a permanent public URL for the file (requires bucket public read).
+
+        Returns:
+            A permanent URL in the format: https://{bucket}.{endpoint}/{file_key}
+        """
+        host = self.endpoint.replace("https://", "").replace("http://", "")
+        return f"https://{self.bucket_name}.{host}/{file_key}"

api/app/core/storage/s3.py

@@ -378,3 +378,12 @@ class S3Storage(StorageBackend):
             logger.error(f"Failed to generate presigned URL for {file_key}: {e}")
             # Return a basic URL format as fallback
             return f"https://{self.bucket_name}.s3.{self.region}.amazonaws.com/{file_key}"
+
+    async def get_permanent_url(self, file_key: str) -> str:
+        """
+        Get a permanent public URL for the file (requires bucket public read).
+
+        Returns:
+            A permanent URL in the format: https://{bucket}.s3.{region}.amazonaws.com/{file_key}
+        """
+        return f"https://{self.bucket_name}.s3.{self.region}.amazonaws.com/{file_key}"