Add non-interactive CLI mode and gitignore for local/runtime artifacts.

Support --team/--channel/--output flags for scripted exports, add renew.sh
wrapper, and exclude config, cookies, results, and sqlite index from git.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -0,0 +1,16 @@
+# Local credentials and session state
+config.json
+cookies.pkl
+
+# Export output and search index
+results/
+mattermost_index.sqlite
+
+# Python
+.venv/
+__pycache__/
+*.py[cod]
+*.pyo
+
+# IDE
+.cursor/