Consolidate stream classes into single module

- Move AttachmentStream and DataStream from separate modules into av/stream.py
- Convert stream.pyx from Cython to pure Python
- Add missing 'options' property to Stream type hints

This consolidation reduces code duplication and simplifies the module
structure without changing the public API.

Author: WyattBlue

av/attachments/__init__.py

@@ -19,8 +19,14 @@ cdef class Stream:
     # Private API.
     cdef _init(self, Container, lib.AVStream*, CodecContext)
     cdef _finalize_for_output(self)
-    cdef _set_time_base(self, value)
     cdef _set_id(self, value)
 
 
 cdef Stream wrap_stream(Container, lib.AVStream*, CodecContext)
+
+
+cdef class DataStream(Stream):
+    pass
+
+cdef class AttachmentStream(Stream):
+    pass