feat: Add SMTP testing and improve Docker setup

Introduce a new feature to test SMTP configuration directly from the settings page. This involves adding a new API endpoint and corresponding UI elements to trigger and display the results of an SMTP test.

Additionally, this commit refactors the Docker setup by consolidating Dockerfiles and removing unnecessary configuration files. The goal is to streamline the build process and reduce image size and complexity.

Dockerfile

@@ -1,15 +0,0 @@
-# Stage 1: Build Frontend
-FROM node:18-alpine as build
-WORKDIR /app
-COPY package*.json ./
-RUN npm install
-COPY . .
-RUN npm run build
-
-# Stage 2: Serve with Nginx
-FROM nginx:alpine
-COPY --from=build /app/dist /usr/share/nginx/html
-# Copy the nginx configuration file (using the .txt extension as provided in source)
-COPY nginx.txt /etc/nginx/nginx.conf
-EXPOSE 80
-CMD ["nginx", "-g", "daemon off;"]