Add particle-os repository for composefs dependency

- Add repository setup to CI workflow before installing dependencies
- Add repository setup to Dockerfile for composefs package
- Use correct repository key URL and sources.list format
- This allows CI to install composefs from private particle-os registry

.forgejo/workflows/ci.yml

@@ -67,6 +67,10 @@ jobs:
 
       - name: Install dependencies
         run: |
+          # Add particle-os repository for composefs
+          curl -fsSL https://git.raines.xyz/api/packages/particle-os/debian/repository.key -o /etc/apt/keyrings/forgejo-particle-os.asc
+          echo "deb [signed-by=/etc/apt/keyrings/forgejo-particle-os.asc] https://git.raines.xyz/api/packages/particle-os/debian trixie main" >> /etc/apt/sources.list.d/forgejo.list
+          
           apt update -y
           apt install -y --no-install-recommends \
             git curl pkg-config build-essential gnupg wget \