chore(ci): run forgejo jobs on lxc bookworm containers

.forgejo/workflows/ci.yml

@@ -14,6 +14,8 @@ jobs:
   backend-lint:
     name: Backend Linting & Type Checking
     runs-on: lxc
+    container:
+      image: debian:bookworm
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -52,6 +54,8 @@ jobs:
   frontend-check:
     name: Frontend Type Checking & Linting
     runs-on: lxc
+    container:
+      image: debian:bookworm
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -83,6 +87,8 @@ jobs:
   backend-test:
     name: Backend Tests
     runs-on: lxc
+    container:
+      image: debian:bookworm
     # Disabled for now since tests are not integrated yet
     if: false
     steps: