ci(docker): optimize Dockerfiles with pnpm and build cache integration

Switch to `node:22-alpine` for smaller base images. Introduce pnpm cache mounts and utilize `--frozen-lockfile` for faster and more reliable builds. Add Next.js build cache optimizations for `frontend` and `documentation`.

frontend/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker.io/docker/dockerfile:1
+# syntax=docker/dockerfile:1
 
 FROM node:22-alpine AS base
 ENV PNPM_HOME="/pnpm"
@@ -11,11 +11,20 @@ COPY pnpm-lock.yaml pnpm-workspace.yaml package.json ./
 COPY backend/package.json ./backend/
 COPY frontend/package.json ./frontend/
 COPY documentation/package.json ./documentation/
-RUN pnpm install --no-frozen-lockfile
+
+# Montage du cache pnpm
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm install --frozen-lockfile
+
 COPY . .
-# On réinstalle après COPY pour s'assurer que tous les scripts de cycle de vie et les liens sont corrects
-RUN pnpm install --no-frozen-lockfile
-RUN pnpm run --filter @memegoat/frontend build
+
+# Deuxième passe avec cache pour les scripts/liens
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm install --frozen-lockfile
+
+# Build avec cache Next.js
+RUN --mount=type=cache,id=next-cache,target=/usr/src/app/frontend/.next/cache \
+    pnpm run --filter @memegoat/frontend build
 
 FROM node:22-alpine AS runner
 WORKDIR /app