Add sponsorship page with Sankey cost breakdown diagram

[devin-ai-integration]

Summary

Adds a new /sponsor page (also accessible at /support) with a Sankey-style cost breakdown diagram that visually shows sponsors how expensive it is to run BMT.

The page includes:

• Sankey flow diagram (pure SVG, no JS dependencies) showing the $68,000+ annual budget flowing from a total bar into four proportional cost categories:
  • Venue & classroom reservations ($50,000+/yr) — 73%
  • Day-of supplies, awards & food ($10,000+/event) — 15%
  • Contest materials & printing ($5,000+/yr) — 7%
  • Digital infrastructure & platform ($3,000+/yr) — 5%
• Left column with bullet points explaining what donations fund
• 501(c)(3) nonprofit callout box
• CTA section with "Become a Sponsor" (email) and "Make a Donation" (links to /give) buttons
• Color legend with percentage breakdown
• Hover effects on the Sankey flows for interactivity

New files:

• content/sponsor.md — page content and cost data in TOML frontmatter
• templates/sponsor.html — custom template with the Sankey SVG

Review & Testing Checklist for Human

• Visit /sponsor and verify the Sankey diagram renders correctly and text is readable
• Test on mobile viewport — the two-column layout should stack vertically on small screens
• Verify the "Become a Sponsor" mailto link goes to finance@berkeley.mt
• Verify the "Make a Donation" button redirects correctly via /give
• Check that the cost figures ($50k, $10k, $5k, $3k) and total ($68k) are accurate

Notes

• The diagram is pure inline SVG with CSS hover effects — no JavaScript libraries needed
• Cost data is stored in the frontmatter of content/sponsor.md for easy future updates
• Page is accessible at both /sponsor and /support via Zola aliases

Link to Devin session: https://app.devin.ai/sessions/16b88411547b41eb850553ce0910c541

[devin-ai-integration]

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