Update render-engine and adopt RedirectPage

[kjaymiller]

Summary

• Bumps render-engine to 2026.5.2a1 (and pins the rest of the deps for reproducibility).
• Switches the five redirect pages (students, community, partnerships, leadership, pycon) from hand-written meta-refresh HTML to the new RedirectPage class introduced in Add support for page redirection. render-engine/render-engine#1161.
• Deletes the now-unused root HTML files that used to back those redirects.
• Fixes the /students target, which previously pointed at the non-existent /student-ambassadors-program.html (extra s).
• Footer: drop the Partnerships/Community links, add a Students Ambassador Program link.

Upstream reference

RedirectPage feature: render-engine/render-engine#1161

Test plan

• uv sync resolves the new lockfile cleanly
• uv run render-engine build succeeds
• output/pycon.html, output/community.html, output/partnerships.html, output/leadership.html, output/students.html each contain a <meta http-equiv="Refresh" ...> pointing at the expected target
• /students redirect lands on /student-ambassador-program.html (singular)
• Footer renders the new Students Ambassador Program link

🤖 Generated with Claude Code

[dragid10]

One more merge conflict 👀

[kjaymiller]

@dragid10 - done

[kjaymiller]

@dragid10 the failing test is for the redirect test logic which is corrected in #914

[dragid10]

Overall looks good, just had a question about dependency pinning going forward.

[dragid10]

Low Care Amount: Is pyyaml explicitly imported anywhere? If not, I'd probably not include it in the top-level packages. But if we are including it solve a CVE, then we could do pyyaml~=6.0 to always allow for patch version pickups.

[kjaymiller]

It is. IIRC we run deptry so all the items that are in the dependencies are directly called in the app.

[dragid10]

Medium Care Amount: I'm curious as to why we're pinning explicit versions. I mean I know that its definitely the most reproducible, but I feel like most of these could benefit from allowing patch versions to pick up vulnerability fixes in the future

[kjaymiller]

explicit versions is just based on historical presedent as render-engine ran into parser errors because we didn't explicitly pin our versions. FMI: render-engine/render-engine-markdown#9 (review)

[dragid10]

makes perfect sense. I do think a good medium path would still be adding constraints that aren't exact version pins, but that is a future consideration!