fix: add future annotations import to discovery.py (#229)

Adds 'from __future__ import annotations' to spec/discovery.py for
Python 3.9+ compatibility with type hints.

This completes the Python compatibility fixes that were partially
applied in previous commits. All 26 analysis and spec Python files
now have the future annotations import.

Related: #128

Co-authored-by: Joris Slagter <mail@jorisslagter.nl>

apps/backend/spec/discovery.py

@@ -5,6 +5,8 @@ Discovery Module
 Project structure analysis and indexing.
 """
 
+from __future__ import annotations
+
 import json
 import shutil
 import subprocess