Fix Quartz build to preserve git history for accurate file dates (#105)

## Summary

Fixes the "isn't yet tracked by git, dates will be inaccurate" warnings in the Build docs step by restructuring how Quartz builds the documentation.

## Problem

Previously, we copied docs into Quartz's content folder. Since this was inside a fresh Quartz clone with no history of our files, the `CreatedModifiedDate` plugin couldn't determine accurate dates.

## Solution

Build Quartz from within the blumeops repo instead:
1. Copy Quartz's build system (quartz/, package.json, etc.) into the workspace
2. Symlink `content` -> `docs` (preserves git history)
3. Symlink `docs/CHANGELOG.md` -> `../CHANGELOG.md`
4. Build from workspace root where git can trace file history
5. Clean up artifacts after creating tarball

## Deployment and Testing

- [ ] Run build workflow and verify no "not tracked by git" warnings
- [ ] Verify file dates appear correctly on built docs site

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/105

docs/changelog.d/fix-quartz-git-dates.doc.md

@@ -0,0 +1 @@
+Fix misc changelog fragment type to show content (was showing empty entries)

docs/changelog.d/fix-quartz-git-dates.infra.md

@@ -0,0 +1 @@
+Fix Quartz build to preserve git history for accurate file dates