feat: local storage logic & endpoints

app/domain/errors.py

@@ -61,3 +61,19 @@ class DependencyUnavailableError(DomainError):
     """
 
     code = "dependency_unavailable"
+
+
+class StorageError(DomainError):
+    """File storage operation failed."""
+
+    code = "storage_error"
+
+
+class RangeNotSatisfiableError(DomainError):
+    """Requested byte range cannot be satisfied."""
+
+    code = "range_not_satisfiable"
+
+    def __init__(self, total_size: int) -> None:
+        super().__init__("Requested range is not satisfiable.")
+        self.total_size = total_size