feat(dev-session): Containerize dev session manager

This commit introduces a containerized workflow for the development session manager (dev_session.py).

- Dockerization: Added gemini.Dockerfile to create a self-contained environment with all Python dependencies, removing the need for manual host setup.
- Start Script: Updated start-gemini.sh to build and run the container, executing dev_session.py as the entrypoint.
- Session Management: Implemented --done flag to properly terminate a session, update the Notion task status, and clean up the git hook.
- Notion Integration: Created and integrated notion_commit_hook.py which is automatically installed/uninstalled to post commit messages to the active Notion task.
- Documentation: Updated README_dev_session.md to reflect the new container-based setup, usage, and features.

gemini.Dockerfile

@@ -11,6 +11,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Python-Abhängigkeiten für dev_session.py installieren
+RUN pip3 install requests python-dotenv --break-system-packages
+
 # Installieren der von Ihnen gefundenen, korrekten Gemini CLI global
 RUN npm install -g @google/gemini-cli