fix Python 3.9 compatibility (str | None union syntax)

parser.py and update_mods.py were missing
'from __future__ import annotations', causing a TypeError on
Python < 3.10 when the X | Y union syntax is evaluated at runtime.
All other modules already had the import.

Also lowers MIN_PYTHON from 3.11 to 3.9 -- the toolchain does not
use any Python 3.10/3.11-specific stdlib features beyond the union
annotation syntax which is now handled by the future import.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

check_deps.py

@@ -13,7 +13,7 @@ import sys
 
 # Must not import arma_modlist_tools here — that's what we're checking FOR.
 
-MIN_PYTHON = (3, 11)
+MIN_PYTHON = (3, 9)
 REQUIRED_PACKAGES = ["requests", "tqdm"]