Fix empty tag in dispatched Windows builds

The workflow_dispatch input was accessed as github.event.inputs.tag
which can be empty depending on the Gitea runner. Now tries both
inputs.tag (modern syntax) and github.event.inputs.tag as fallback,
with a final fallback to the latest matching git tag.

Also switched Windows Determine-tag steps from PowerShell to bash
(via Git Bash) for consistency with the other platforms.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-app-windows.yml

@@ -16,14 +16,17 @@ jobs:
     steps:
       - name: Determine tag
         id: tag
-        shell: powershell
+        shell: bash
         run: |
-          $TAG = "${{ github.event.inputs.tag }}"
-          if (-not $TAG) {
-            $TAG = (git ls-remote --tags --sort=-v:refname origin 'refs/tags/v*' | Select-Object -First 1) -replace '.*refs/tags/', ''
-          }
-          Write-Host "Building for tag: ${TAG}"
-          echo "tag=${TAG}" >> $env:GITHUB_OUTPUT
+          TAG="${{ inputs.tag }}"
+          if [ -z "$TAG" ]; then
+            TAG="${{ github.event.inputs.tag }}"
+          fi
+          if [ -z "$TAG" ]; then
+            TAG=$(git ls-remote --tags --sort=-v:refname origin 'refs/tags/v*' | head -1 | sed 's|.*refs/tags/||')
+          fi
+          echo "Building for tag: ${TAG}"
+          echo "tag=${TAG}" >> $GITHUB_OUTPUT
 
       - uses: actions/checkout@v4
         with: