feat: port remaining cohort scripts and make reusable

- Port 19 cohort scripts from /home/naomi/docs/cohort/
- Replace all hardcoded tokens and dotenv usage with os.environ
- Add pandas==3.0.1 dependency
- Add E501 to ruff ignore list for Discord message string content
- Make remove_resigned_members.py reusable (empty RESIGNED_IDS constant)
- Make update_roster_messages.py reusable (iterates all teams from JSON)
- Exclude 12 one-off/event-specific scripts as non-reusable

python/pyproject.toml

@@ -79,6 +79,8 @@ ignore = [
     "DTZ001",
     # Ambiguous variable names - context makes it clear
     "E741",
+    # Long lines in string literals (Discord messages, URLs)
+    "E501",
 ]
 
 [tool.ruff.lint.pydocstyle]