docs: Bring documentation (fully) up to date

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reopens the erroneously closed #609. This PR fills in incomplete pages which were punted as part of #613.

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Summary

• Migrate documentation from Sphinx/RST to MkDocs Material with full content covering all MaveDB features across 30+ pages organized into Getting Started, Finding Data, Submitting Data, MaveMD, Programmatic Access, and Reference sections
• Add build pipeline (scripts/build-docs.sh) that builds MkDocs and copies output to public/docs/mavedb/ for Vite bundling; runs automatically in npm run dev, build, and preview
• Add npm run docs script for local docs development with hot-reload
• Use use_directory_urls: false for compatibility with S3/CloudFront and Vite dev server
• Update all Vue component doc links (ScoreSetCreator, DocumentationView) to new /docs/mavedb/ paths
• Enhance docs with MkDocs Material features: screenshots, Mermaid diagrams, admonitions, abbreviation tooltips (glossary), code copy buttons, instant navigation, and content tooltips
• Remove old Sphinx HTML files, RST sources, and Sphinx dependencies

Test plan

• Run npm run dev and verify docs load at https://127.0.0.1:8081/docs/mavedb/index.html
• Navigate between docs pages and verify internal links work
• Verify Vue app doc links in score set creation wizard point to correct pages
• Run npm run build and verify docs are included in dist/docs/mavedb/
• Run npm run docs and verify MkDocs dev server starts
• Spot-check screenshots, Mermaid diagrams, admonitions, and abbreviation tooltips render correctly
• Verify old Sphinx URLs (/docs/mavedb/record_types.html, etc.) no longer conflict

AI Involvement

• Model: Claude Opus 4.6

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We might consider removing built docs from source control, given we already track content in the /docs directory, which will deterministically build content in /public/docs/mavedb.