Update roadmap after first beta

[Zhortein]

Objective

Update the roadmap after the first beta release.

Scope

• Mark 0.27 - First beta preparation as completed.
• Mention published tag v0.3.0-beta.1.
• Clarify what beta means for the project.
• Update current limitations.
• Set next roadmap direction.
• Keep later ideas coherent.

Acceptance criteria

• Roadmap reflects first beta release.
• Next milestone direction is clear.
• Known limitations are accurate.
• QA passes.