feat: enrich schedule table with course metrics and foundational filter

[ndenissov]

This PR brings some quality-of-life improvements to the Schedule view, allowing students to evaluate courses without constantly switching back to the main list.

Changes include:

• Added Difficulty, Workload, and Rating columns to the schedule table (stats are fetched alongside the static course data).
• Made the new metric headers sortable to easily compare available classes.
• Added a Foundational courses only toggle to filter the master list. To keep the UI clean, this toggle hides automatically when a specific specialization is selected.
• Made the rating cell clickable so it links directly to the detailed reviews page (/course/[courseId]).
• Slightly widened the table layout to comfortably fit the new data.

[vercel]

@ndenissov is attempting to deploy a commit to the OMShub Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

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