Upgrade HugoBlox workflows and fix build

[eaogorman]

Summary

• Updates GitHub Actions deploy workflow to use Hugo 0.156.0 (was 0.148.2, which is incompatible with current HugoBlox modules)
• Adds new reusable build.yml workflow that reads Hugo version from hugoblox.yaml
• Fixes invalid date format in GRC event (2024-22-05 → 2024-05-22)
• Adds go.sum for reproducible Hugo module builds
• Migrates events content to match upgraded HugoBlox schema

Test plan

• Local hugo --minify build succeeds (81 pages)
• GitHub Actions build completes successfully after merge
• Site deploys and loads at https://eaogorman.github.io/

[eaogorman]

• Workflow files: updated deploy.yml updates Hugo version for build, new build.yml reusable workflow, fix the build and nothing else
• GRC event date fix: 2024-22-05 to 2024-05-22, was already broken/unparseable, now correct
• go.sum: lock file for reproducible module resolution, no content impacted
• Event frontmatter format: minor schema migration in events/ files, event: event_name : , date_end: event_end; same data, field names matching upgraded HugoBlox schema
• .gitignore: adds events.backup/
• Author data: Google Scholar link syntax fix (already on upgrade branch)

No content removed, no pages disappear, no layout changes