@chore(release): bump version to 3.9.0 (issue #112)

- deploy.yml: VERSION 3.8.0 -> 3.9.0 (docker image tag for next push to main)
- NavMenu.razor: visible version v3.8.0 -> v3.9.0
- CampaignTemplatesNavigationTests.NavMenu_ShouldExposeCurrentProjectVersion: expected v3.7.1 -> v3.9.0 (was broken since 3.8.0 bump in commit 71080ae)
- RELEASE_NOTES.md: prepend Minor 3.9.0 entry (Discord wizard, issue #112) with full file inventory
- docs/review-brief.md: code-review spec for the verifier session

Build green (0 warnings, 0 errors), dotnet format clean.

.gitea/workflows/deploy.yml

@@ -6,7 +6,7 @@ on:
       - main 
 
 env:
-  VERSION: 3.8.0
+  VERSION: 3.9.0
 
 jobs:
   # ЧАСТЬ 1: Собираем образы и кладем в Gitea (чтобы делиться с ребятами)