Fix CI workflows for Gitea/Forgejo runner

- Replace GitHub actions with Forgejo equivalents:
  - actions/checkout@v4 -> code.forgejo.org/actions/checkout@v4
  - actions/upload-artifact@v4 -> code.forgejo.org/actions/upload-artifact@v3
- Fixes problem-matcher.json path errors on Gitea runner
- Fixes artifact upload compatibility issues

.gitea/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
           node --version
 
       - name: Checkout repository
-        uses: https://github.com/actions/checkout@v4
+        uses: https://code.forgejo.org/actions/checkout@v4
         with:
           submodules: recursive
           fetch-depth: 0
@@ -77,7 +77,7 @@ jobs:
 
       - name: Upload test logs
         if: always()
-        uses: https://github.com/actions/upload-artifact@v4
+        uses: https://code.forgejo.org/actions/upload-artifact@v3
         with:
           name: test-logs
           path: |

.gitea/workflows/release.yml

@@ -37,7 +37,7 @@ jobs:
           node --version
 
       - name: Checkout repository
-        uses: https://github.com/actions/checkout@v4
+        uses: https://code.forgejo.org/actions/checkout@v4
         with:
           submodules: recursive
           fetch-depth: 0
@@ -80,7 +80,7 @@ jobs:
           ls -lah package/rattler-build/linux/*-SHA256.txt 2>/dev/null || echo "No SHA256 files found"
 
       - name: Upload AppImage artifact
-        uses: https://github.com/actions/upload-artifact@v4
+        uses: https://code.forgejo.org/actions/upload-artifact@v3
         with:
           name: kindred-create-appimage
           path: |