fix(ci): run docker workflow only on released events

[Teagan42]

What

• trigger Docker publish workflow only when a GitHub release is actually released
• bump package version to 0.4.3

Why

• avoid running the Docker build on release creation or deletion

Affects

• CI/CD workflow for Docker image publishing
• project versioning

Testing

• uv run ruff check .
• uv run pytest

Documentation

• none required

---

https://chatgpt.com/codex/tasks/task_e_68bfad0d95848328bc28b52e05142950

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
mcp_plex
loader.py	186	16	91%	32–34, 301, 304–307, 352–361, 599, 605
server.py	190	22	88%	75, 93–94, 205–221, 313, 317, 337–341, 374
TOTAL	478	38	92%

Tests	Skipped	Failures	Errors	Time
19	0 💤	0 ❌	0 🔥	11.505s ⏱️