feat: add OAuth1 PIN-based token save script

[yasaka57]

Summary

• Adds save_tokens.py: a one-time helper that runs the OAuth1 PIN-based consent flow and writes X_OAUTH_ACCESS_TOKEN / X_OAUTH_ACCESS_TOKEN_SECRET directly into .env
• Enables automated or scheduled scripts to authenticate with static credentials, without re-running the browser-based OAuth flow on every execution
• No new dependencies — uses requests-oauthlib and python-dotenv already listed in requirements.txt

How it works

1. python save_tokens.py
2. Open the printed URL in a browser and authorize the app
3. Paste the displayed PIN into the terminal
4. Tokens are written to .env automatically

Test plan

• Confirm X_OAUTH_ACCESS_TOKEN and X_OAUTH_ACCESS_TOKEN_SECRET are populated in .env after running the script
• Confirm a subsequent createPosts call succeeds with the saved credentials without re-running the flow

🤖 Generated with Claude Code

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