dev: add Dockerfile.dev + allow content-edits API from dev.mamadaevv.site

Dockerfile.dev

@@ -0,0 +1,9 @@
+# Dev environment: serves public/ with BrowserSync + content-edits API (port 4175)
+FROM node:20-alpine
+WORKDIR /app
+COPY package*.json ./
+RUN npm install
+COPY . .
+RUN npm run build:pages
+EXPOSE 4175
+CMD ["npm", "run", "serve"]