fix(ci): use explicit NVM_DIR to load nvm in non-interactive shell

Gitea Actions runs steps in a non-interactive shell that does not
source .bashrc. Use the explicit NVM_DIR path to load nvm.

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

.gitea/workflows/deploy-ui.yml

@@ -20,7 +20,8 @@ jobs:
 
       - name: Set up Node.js
         run: |
-          source ~/.nvm/nvm.sh
+          export NVM_DIR="${HOME}/.nvm"
+          [ -s "${NVM_DIR}/nvm.sh" ] && . "${NVM_DIR}/nvm.sh"
           nvm install --lts
           echo "$(dirname "$(nvm which current)")" >> "$GITHUB_PATH"