fix(ci): validate docs before deployment

[ManukMinasyan]

Summary

• restore better-sqlite3 to Docus 5.12.3's supported 12.x range
• build documentation on every pull request
• deploy the exact artifact produced by the verified build
• group only minor and patch Dependabot updates
• keep major dependency updates separate for manual review
• serialize build and deployment to prevent stale deployments

Why

PR #170 upgraded better-sqlite3 to 13.0.3, outside Docus's declared peer range.

PHP CI passed because it never installed or built docs/. The deployment later failed during npm ci.

Verification

• documentation installation and generation passed with Node 24 and npm 11
• actionlint passed
• zizmor passed with no findings
• Dependabot schema validation passed
• PHP suite passed with 161 tests and 20,685 assertions
• independent code review returned ready to merge

Follow-up

Require the Docs build check on 4.x, including administrator merges.

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