feat: presentation-ready chart export (PNG/PDF) with definitions baked in

[William-Hill]

Context

From AASCU Intermediary feedback session (see docs/aascu_intermediary_feedback_summary.md, pain point C):

"I cannot present the same graphs that we need to do my supervisor. It doesn't make sense because they're not clear... So what I had to do was I had to sort of get the data and then sort of get visualized on my own."

"I just went by each data point and then I had to copy that number and then into the Excel spreadsheet and then sort of come up with visualizations."

CSV export already exists (components/export-button.tsx, #15), but IR staff still rebuild charts in Excel because PDP-style charts aren't shareable upward. Closing this loop turns "data tool" into "tool I can present from."

Goal

Every chart in the dashboard exports as a presentation-ready image (PNG and PDF) with title, definitions, data source, and date stamp embedded.

Scope

• "Export" menu on every chart with options: CSV (existing), PNG, PDF
• Exported image includes:
  • Chart title
  • Inline metric definition (1-2 lines, pulled from glossary — see #[glossary issue])
  • "Data source: , generated "
  • Bishop State (or institution) branding
• Exports use the same Recharts SVG, rasterized server-side or client-side
• Bonus: "Copy as image" for paste-into-deck workflows

Out of scope

• Native PowerPoint (.pptx) export — defer to a follow-up issue if requested
• Bulk export of all charts as a single deck (separate issue)

Acceptance criteria

• PNG export works on every chart in the dashboard
• PDF export works on every chart
• Exported assets contain definition text and date stamp
• File naming convention: <institution>_<chart-name>_<YYYY-MM-DD>.<ext>

Dependencies

• Glossary issue (definitions to embed)