Replace GitHub Actions with Gitea Actions

- Remove all GitHub Actions workflows (21 files)
- Remove GitHub problem matchers
- Add Gitea build workflow (push/PR to main)
- Add Gitea release workflow (version tags)
- Use pixi for dependency management
- Configure ccache for build acceleration
- Use 16 build threads for debian-host runner
- Update .gitignore to allow .gitea/ directory

.gitea/workflows/build.yml

@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+name: Build and Test
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: debian-host
+
+    env:
+      CCACHE_DIR: /var/cache/ccache/kindred-create
+      CCACHE_COMPRESS: "true"
+      CCACHE_COMPRESSLEVEL: "5"
+      CCACHE_MAXSIZE: "2G"
+      CCACHE_NODIRECT: "true"
+      CCACHE_NOHASHDIR: "true"
+      CCACHE_NOINODECACHE: "true"
+      CCACHE_SLOPPINESS: "include_file_ctime,include_file_mtime,pch_defines,time_macros"
+      CCACHE_COMPILERCHECK: "%compiler% -dumpfullversion -dumpversion"
+
+    steps:
+      - name: Checkout repository
+        uses: https://github.com/actions/checkout@v4
+        with:
+          submodules: recursive
+          fetch-depth: 0
+
+      - name: Install pixi if needed
+        shell: bash
+        run: |
+          if ! command -v pixi &> /dev/null; then
+            curl -fsSL https://pixi.sh/install.sh | bash
+            echo "$HOME/.pixi/bin" >> $GITHUB_PATH
+            export PATH="$HOME/.pixi/bin:$PATH"
+          fi
+          pixi --version
+
+      - name: Prepare ccache
+        shell: bash
+        run: |
+          sudo mkdir -p $CCACHE_DIR
+          sudo chown $(whoami):$(whoami) $CCACHE_DIR
+          pixi run ccache -z
+          pixi run ccache -p
+
+      - name: Configure (CMake)
+        run: pixi run configure-release
+
+      - name: Build
+        run: pixi run cmake --build build/release -j16
+
+      - name: Show ccache statistics
+        run: pixi run ccache -s
+
+      - name: Run C++ unit tests
+        run: pixi run test-release
+
+      - name: Install
+        run: pixi run install-release
+
+      - name: Run Python CLI tests
+        run: pixi run build/release/bin/FreeCADCmd -t 0 || true
+
+      - name: Run GUI tests (headless)
+        run: pixi run xvfb-run build/release/bin/FreeCAD -t 0 || true

.gitea/workflows/release.yml

@@ -0,0 +1,76 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+name: Release Build
+
+on:
+  push:
+    tags: ['v*', 'weekly-*']
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Release tag (e.g., v1.0.0)'
+        required: true
+        type: string
+
+jobs:
+  build-linux-appimage:
+    runs-on: debian-host
+
+    env:
+      CCACHE_DIR: /var/cache/ccache/kindred-create
+      CCACHE_COMPRESS: "true"
+      CCACHE_COMPRESSLEVEL: "5"
+      CCACHE_MAXSIZE: "2G"
+      CCACHE_NODIRECT: "true"
+      CCACHE_NOHASHDIR: "true"
+      CCACHE_NOINODECACHE: "true"
+      CCACHE_SLOPPINESS: "include_file_ctime,include_file_mtime,pch_defines,time_macros"
+      CCACHE_COMPILERCHECK: "%compiler% -dumpfullversion -dumpversion"
+      BUILD_TAG: ${{ github.ref_name || inputs.tag }}
+      MAKE_INSTALLER: "true"
+
+    steps:
+      - name: Checkout repository
+        uses: https://github.com/actions/checkout@v4
+        with:
+          submodules: recursive
+          fetch-depth: 0
+          fetch-tags: true
+
+      - name: Install pixi if needed
+        shell: bash
+        run: |
+          if ! command -v pixi &> /dev/null; then
+            curl -fsSL https://pixi.sh/install.sh | bash
+            echo "$HOME/.pixi/bin" >> $GITHUB_PATH
+            export PATH="$HOME/.pixi/bin:$PATH"
+          fi
+          pixi --version
+
+      - name: Prepare ccache
+        shell: bash
+        run: |
+          sudo mkdir -p $CCACHE_DIR
+          sudo chown $(whoami):$(whoami) $CCACHE_DIR
+          pixi run ccache -z
+
+      - name: Write version info
+        run: python3 package/scripts/write_version_info.py ../freecad_version.txt
+
+      - name: Build release package (AppImage)
+        working-directory: package/rattler-build
+        run: |
+          pixi install
+          pixi run -e package create_bundle
+
+      - name: Show ccache statistics
+        run: pixi run ccache -s
+
+      - name: Upload AppImage artifact
+        uses: https://github.com/actions/upload-artifact@v4
+        with:
+          name: kindred-create-linux-x86_64-${{ env.BUILD_TAG }}
+          path: |
+            package/rattler-build/linux/*.AppImage
+            package/rattler-build/linux/*.AppImage.zsync
+            package/rattler-build/linux/*-SHA256.txt
+          if-no-files-found: warn