Create pinned roadmap issue

[zeevdr]

Description

Create a pinned issue that serves as the public roadmap. Gives external users a single place to see what's planned and where to suggest features.

Acceptance criteria

• Create a "Roadmap" issue listing current milestones and high-level goals
• Pin it to the top of the Issues tab
• Reference it from CONTRIBUTING.md as the place for feature discussion
• Keep it updated as milestones are completed

Notes

• Use checkboxes or a table grouped by milestone
• Link to the GitHub milestones for detailed issue lists
• This is the polite redirect target for "can you add X?" requests