Fix CI workflow: use catthehacker/ubuntu:act-latest for Node.js support

The actions/checkout@v4 action requires Node.js, but python:3.12-slim doesn't include it.
Using catthehacker/ubuntu:act-latest which has both Node.js and Python support.

- Update ci.yaml to use act-compatible image
- Update deploy.yaml to use act-compatible image
- Use actions/setup-python@v5 for Python installation

.forgejo/workflows/ci.yaml

@@ -14,9 +14,13 @@ jobs:
   lint:
     runs-on: docker
     container:
-      image: python:3.12-slim
+      image: catthehacker/ubuntu:act-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
@@ -29,9 +33,13 @@ jobs:
   test:
     runs-on: docker
     container:
-      image: python:3.12-slim
+      image: catthehacker/ubuntu:act-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
@@ -42,9 +50,13 @@ jobs:
   type-check:
     runs-on: docker
     container:
-      image: python:3.12-slim
+      image: catthehacker/ubuntu:act-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip