feat(client): show git-describe version next to the brand logo

Display the app version (output of `git describe --tags`) in the header
beside the gitmost logo: a clean tag renders as `vX.Y.Z`, otherwise the
tag plus commits-since and short hash (e.g. v0.90.1-56-g25975acd).

- vite.config.ts: resolve APP_VERSION from env (Docker/CI) -> git describe
  (local) -> package.json version fallback
- app-header.tsx: render APP_VERSION after the brand block (ml="md"),
  nudge the Home nav group (ml={50} -> "xl")
- Dockerfile: accept APP_VERSION build-arg in the builder stage (.git is
  excluded from the build context)
- CI: pass APP_VERSION build-arg — release.yml uses the tag, develop.yml
  computes git describe with fetch-depth: 0
- nx.json: add APP_VERSION to the build target inputs so the cache
  invalidates when the version changes

.github/workflows/release.yml

@@ -50,6 +50,8 @@ jobs:
         with:
           context: .
           platforms: ${{ matrix.platform }}
+          build-args: |
+            APP_VERSION=${{ env.VERSION }}
           outputs: type=image,name=${{ env.IMAGE }},push-by-digest=true,name-canonical=true,push=true
           cache-from: type=gha,scope=${{ matrix.suffix }}
           cache-to: type=gha,scope=${{ matrix.suffix }},mode=max,ignore-error=true
@@ -76,6 +78,8 @@ jobs:
         with:
           context: .
           platforms: ${{ matrix.platform }}
+          build-args: |
+            APP_VERSION=${{ env.VERSION }}
           push: false
           tags: |
             ${{ env.IMAGE }}:latest