[BUG] Error saving config in Docker container - allow config persistance

[sentisso]

When running claude-devtools in Docker, it's not possible to save the user config claude-devtools-config.json because of the read-only mount in docker-compose.yml:

    volumes:
      - ${CLAUDE_DIR:-~/.claude}:/data/.claude:ro

This results in an error when trying to save settings in the UI:

[Service:ConfigManager] Error saving config: Error: EROFS: read-only file system, open '/data/.claude/claude-devtools-config.json'

To Reproduce
Steps to reproduce the behavior:

1. Run the Docker container with default settings
2. Go to settings and edit anything (e.g., change the theme to light)
3. Changes are applied but only in the current runtime:
   • docker logs produce the error log above
4. Restart the Docker container
5. Re-open claude-devtools, changes are not persisted across container restarts

Expected behavior
The claude-devtools-config.json file should have read-write permissions, in order to persist changes:

    volumes:
      - ${CLAUDE_DIR:-~/.claude}:/data/.claude:ro
      - ${CLAUDE_DIR:-~/.claude}/claude-devtools-config.json:/data/.claude/claude-devtools-config.json:rw

[sentisso]

Created a PR with a fix at #179