Add Docker and Gitea workflow configurations for Talks slides deployment

- Introduced .dockerignore to exclude unnecessary files from Docker builds.
- Added build-and-push.yaml workflow for automated image building and Helm chart deployment on changes to specific paths.
- Created Dockerfile for building a static site with Nginx, including configuration for serving slides.
- Established Helm chart structure in talks-slides-dist for managing deployment configurations and resources.
- Removed outdated GitHub Actions workflows to streamline CI/CD processes.

.gitea/workflows/build-and-push.yaml

@@ -0,0 +1,128 @@
+name: Talks slides — image & chart
+
+# Build image + chart quand le site statique (portail, decks, toolchain) ou l’infra change.
+on:
+  push:
+    branches: [main, master, develop, cicd]
+    tags: ['v*']
+    paths:
+      - 'server/**'
+      - 'talks-slides-dist/**'
+      - '.gitea/workflows/**'
+      - 'portal/**'
+      - 'slides/**'
+      - 'tools/**'
+      - 'package.json'
+      - 'package-lock.json'
+      - '.dockerignore'
+  pull_request:
+    branches: [main, master, develop]
+    paths:
+      - 'server/**'
+      - 'talks-slides-dist/**'
+      - '.gitea/workflows/**'
+      - 'portal/**'
+      - 'slides/**'
+      - 'tools/**'
+      - 'package.json'
+      - 'package-lock.json'
+      - '.dockerignore'
+
+env:
+  # GIT_DEFAULT_HASH: sha256
+  DOCKER_HOST: 'unix:///var/run/docker.sock'
+  DOCKER_CERT_PATH: '/certs/client'
+  IMAGE_REGISTRY: git.specificat.io
+  IMAGE_NAME: specificat.io/talks-slides
+  # Même registre OCI Helm que les autres charts (ex. knowledge-mcp).
+  HELM_OCI_REPOSITORY: oci://git.specificat.io/specificat.io
+  HELM_DIR: ./talks-slides-dist
+
+jobs:
+  vars:
+    runs-on: ubuntu-latest
+    outputs:
+      version: ${{ steps.out.outputs.version }}
+    steps:
+      - id: out
+        env:
+          RUN_NUMBER: ${{ github.run_number }}
+          REF_NAME: ${{ github.ref_name }}
+        run: |
+          if [[ "${{ github.ref }}" == refs/tags/* ]]; then
+            echo "version=${REF_NAME#v}" >> $GITHUB_OUTPUT
+          else
+            echo "version=0.0.${RUN_NUMBER}" >> $GITHUB_OUTPUT
+          fi
+
+  build-image:
+    runs-on: ubuntu-latest
+    name: Build container image
+    needs: vars
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/login-action@v3
+        if: github.event_name == 'push'
+        with:
+          registry: ${{ env.IMAGE_REGISTRY }}
+          username: ${{ secrets.CI_USER }}
+          password: ${{ secrets.CI_TOKEN }}
+      - name: Build and push image
+        if: github.event_name == 'push'
+        env:
+          VERSION: ${{ needs.vars.outputs.version }}
+        run: |
+          set -euo pipefail
+          IMAGE="${IMAGE_REGISTRY}/${IMAGE_NAME}:${VERSION}"
+          docker build -f server/Dockerfile -t "${IMAGE}" .
+          docker push "${IMAGE}"
+          if [[ "${{ github.ref }}" == "refs/heads/main" ]]; then
+            docker tag "${IMAGE}" "${IMAGE_REGISTRY}/${IMAGE_NAME}:latest"
+            docker push "${IMAGE_REGISTRY}/${IMAGE_NAME}:latest"
+          fi
+      - name: Build image (PR, no push)
+        if: github.event_name == 'pull_request'
+        run: |
+          set -euo pipefail
+          docker build -f server/Dockerfile -t talks-slides:ci .
+
+  helm:
+    runs-on: ubuntu-latest
+    name: Helm chart
+    needs: vars
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Helm
+        run: |
+          set -euo pipefail
+          curl -fsSL -o helm.tgz --user "${{ secrets.CI_USER }}:${{ secrets.CI_TOKEN }}" \
+            "https://git.specificat.io/api/packages/Specificat.io/generic/helm/4.1.1/helm-v4.1.1-linux-amd64.tar.gz"
+          tar -xzf helm.tgz
+          sudo mv linux-amd64/helm /usr/local/bin/helm
+          helm version
+      # Chart publié avec le même tag que l’image (évite latest / oubli de --set au déploiement).
+      - name: Aligner slides.image.tag sur la version build
+        env:
+          VERSION: ${{ needs.vars.outputs.version }}
+        run: |
+          set -euo pipefail
+          f="${HELM_DIR}/values.yaml"
+          sed -i 's|^    tag: ".*"|    tag: "'"${VERSION}"'"|' "$f"
+          grep -E '^    tag:' "$f" || true
+      - name: Helm lint & template
+        run: |
+          set -euo pipefail
+          helm lint "${HELM_DIR}"
+          helm template talks-slides "${HELM_DIR}"
+      - name: Package and push chart (OCI)
+        if: github.event_name == 'push'
+        env:
+          VERSION: ${{ needs.vars.outputs.version }}
+        run: |
+          set -euo pipefail
+          helm package "${HELM_DIR}" --version "${VERSION}" --app-version "${VERSION}"
+          helm registry login "${IMAGE_REGISTRY}" -u "${{ secrets.CI_USER }}" -p "${{ secrets.CI_TOKEN }}"
+          helm push "talks-slides-chart-${VERSION}.tgz" "${HELM_OCI_REPOSITORY}"