docs: add release notes for v0.1.0–v0.4.0, v0.6.0 and v0.7.0

Backfill notes for versions that had a tag but no release page, so
every version up to v0.7.1 has a GitHub/Gitea release. Tag v0.7.0 at
45b27d5 (was missing).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/release-notes/v0.7.0.md

@@ -0,0 +1,26 @@
+# v0.7.0 — Menu bar & customizable quick toolbar
+
+## ✨ New features
+
+**Menu bar**
+* Every feature is now in a menu, grouped by File / View / Measure / Transform / Tools — no more hunting through one long row of buttons.
+
+**Quick toolbar you can customize**
+* The toolbar now holds only the buttons you use most. Pick which ones under **Quick Bar → Customize**; your choice is remembered next time.
+
+**Tidier section controls**
+* The section axis/position bar only appears while section view is on, so it no longer takes up space.
+
+**About dialog**
+* **Help → About** shows the version and a plain-language history of what each release brought.
+
+## 📦 Downloads
+
+Source only — no prebuilt binaries were published for this version. For a ready-to-run build, grab the [latest release](https://github.com/ETWen/STPViewer/releases/latest).
+
+## 🔗 Links
+
+* [Architecture](https://github.com/ETWen/STPViewer/blob/main/ARCHITECTURE.md)
+* [README](https://github.com/ETWen/STPViewer/blob/main/README.md)
+
+**Full changelog:** [v0.6.0...v0.7.0](https://github.com/ETWen/STPViewer/compare/v0.6.0...v0.7.0)