Add Dockerfile, .dockerignore, and captain-definition for container setup

.dockerignore

@@ -0,0 +1,7 @@
+node_modules
+.svelte-kit
+build
+.git
+.env
+.env.*
+npm-debug.log*

Dockerfile

@@ -0,0 +1,15 @@
+FROM node:22-alpine AS build
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+
+FROM nginx:1.27-alpine
+
+COPY --from=build /app/build /usr/share/nginx/html
+
+EXPOSE 80

captain-definition

@@ -0,0 +1,4 @@
+{
+  "schemaVersion": 2,
+  "dockerfilePath": "./Dockerfile"
+}