fix(ci): use shallow tag-only fetch to avoid 504 timeout

The previous `git fetch --tags` triggers full history negotiation
against the upstream FreeCAD-derived repo (~45k commits), causing
HTTP 504 gateway timeouts on the Gitea instance.

Replace with a depth=1 refspec fetch that pulls only tag refs
without negotiating reachable objects behind them. This is
sufficient for `git describe --tags --always` to resolve a
version string.

.gitea/workflows/build.yml

@@ -37,7 +37,7 @@ jobs:
           fetch-depth: 1
 
       - name: Fetch tags (for git describe)
-        run: git fetch --tags --no-recurse-submodules origin
+        run: git fetch --no-recurse-submodules --depth=1 origin '+refs/tags/*:refs/tags/*'
 
       - name: Install pixi
         run: |