chore: add Dockerfile and devcontainer configuration for Hugo theme development

.devcontainer/Dockerfile

@@ -0,0 +1,21 @@
+FROM mcr.microsoft.com/devcontainers/javascript-node:24
+
+# Install Hugo Extended
+ARG HUGO_VERSION
+RUN curl -sLJO "https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.tar.gz" \
+  && tar -C /usr/local/bin -xf "hugo_extended_${HUGO_VERSION}_linux-amd64.tar.gz" hugo \
+  && rm "hugo_extended_${HUGO_VERSION}_linux-amd64.tar.gz"
+
+# Install Dart Sass
+ARG DART_SASS_VERSION
+RUN curl -sLJO "https://github.com/sass/dart-sass/releases/download/${DART_SASS_VERSION}/dart-sass-${DART_SASS_VERSION}-linux-x64.tar.gz" \
+  && tar -C /usr/local -xf "dart-sass-${DART_SASS_VERSION}-linux-x64.tar.gz" \
+  && ln -s /usr/local/dart-sass/sass /usr/local/bin/sass \
+  && rm "dart-sass-${DART_SASS_VERSION}-linux-x64.tar.gz"
+
+# Install Go
+ARG GO_VERSION
+RUN curl -sLJO "https://go.dev/dl/go${GO_VERSION}.linux-amd64.tar.gz" \
+  && tar -C /usr/local -xf "go${GO_VERSION}.linux-amd64.tar.gz" \
+  && rm "go${GO_VERSION}.linux-amd64.tar.gz"
+ENV PATH="/usr/local/go/bin:${PATH}"

.devcontainer/devcontainer.json

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+{
+  "name": "FixIt Theme",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "args": {
+      "HUGO_VERSION": "0.158.0",
+      "DART_SASS_VERSION": "1.99.0",
+      "GO_VERSION": "1.24.4"
+    }
+  },
+  "postCreateCommand": "pnpm install",
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "budparr.language-hugo-vscode",
+        "kaellarkin.hugo-shortcode-syntax",
+        "lruihao.hugo-partials-refs",
+        "tamasfe.even-better-toml",
+        "casualjim.gotemplate",
+        "SomewhatStationery.some-sass"
+      ]
+    }
+  }
+}