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- Removed outdated GitHub Actions workflows to streamline CI/CD processes.

server/Dockerfile

@@ -0,0 +1,37 @@
+# syntax=docker/dockerfile:1
+# Image statique : build npm (VitePress + Slidev) puis nginx non-root.
+FROM node:22-bookworm-slim AS builder
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+# npm 10 (image officielle) et npm 11 (lock généré localement) divergent sur la validation du lock ; `install` reste déterministe via package-lock.
+RUN npm install
+
+COPY . .
+RUN npm run build
+
+# Même arborescence que tools/static-preview.mjs : portail à la racine, decks sous slides/<slug>/
+RUN set -eux \
+  && mkdir -p /opt/site \
+  && cp -a dist-portal/. /opt/site/ \
+  && for d in dist-*; do \
+       [ -d "$d" ] || continue; \
+       [ "$d" = "dist-portal" ] && continue; \
+       slug="${d#dist-}"; \
+       mkdir -p "/opt/site/slides/${slug}"; \
+       cp -a "${d}/." "/opt/site/slides/${slug}/"; \
+     done
+
+FROM nginxinc/nginx-unprivileged:stable-alpine
+
+ARG UID=101
+ARG GID=101
+
+USER root
+COPY --from=builder /opt/site /usr/share/nginx/html
+COPY server/nginx/default.conf /etc/nginx/conf.d/default.conf
+RUN chown -R "${UID}:${GID}" /usr/share/nginx/html
+
+USER ${UID}
+EXPOSE 8080
+CMD ["nginx", "-g", "daemon off;"]

server/nginx/default.conf

@@ -0,0 +1,22 @@
+server {
+    listen 8080;
+    server_name localhost;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Portail VitePress (fichiers statiques + clean URLs)
+    location / {
+        try_files $uri $uri/ $uri.html =404;
+    }
+
+    # Slidev : /slides/<slug> ou /slides/<slug>/ → première planche (comme static-preview.mjs)
+    # $http_host conserve le port client (reverse proxy, docker -p host:8080).
+    location ~ ^/slides/([^/]+)/?$ {
+        return 302 $scheme://$http_host/slides/$1/1$is_args$args;
+    }
+
+    # Decks Slidev : assets et routes SPA (/1, /2, …)
+    location ~ ^/slides/(?<slug>[^/]+)(?<rest>/.*)$ {
+        try_files $uri $uri/ /slides/$slug/index.html;
+    }
+}