Fix Windows CI PowerShell vs bash error

- Add 'shell: bash' to Install dependencies step
- Resolves PowerShell syntax error on Windows: "Missing '(' after 'if' in if statement"
- Windows runners default to PowerShell but step uses bash syntax
- Ensures consistent bash shell usage across all platforms (macOS, Linux, Windows)
- Matches pattern already used in other CI steps

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: miriamkw

.github/workflows/ci.yml

@@ -45,6 +45,7 @@ jobs:
           swift-version: "5.10"
 
       - name: Install dependencies
+        shell: bash
         run: |
           python -m pip install --upgrade pip
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi