Consolidate CI and deployment workflows

Add a deploy workflow that builds and pushes the Docker image from
the server working directory and runs docker compose on main. Trim
CI to a focused Node build in an alpine container (apk deps,
npm ci, npm run build) and remove the old docker workflow. Simplify
Dockerfile to a builder+runtime flow (npm ci, npm prune,
copy node_modules) and make docker-compose use the registry image
and proxy network.

Dockerfile

@@ -1,37 +1,26 @@
-# Stage 1: Build the Astro app
+# Stage 1: Build
 FROM node:20-alpine AS builder
 
 WORKDIR /app
 
-# Install build dependencies for native modules (e.g. better-sqlite3)
+# Native module build deps (better-sqlite3)
 RUN apk add --no-cache python3 make g++
 
 COPY package*.json ./
-RUN npm install
+RUN npm ci
 
 COPY . .
-RUN npm run build
+RUN npm run build && npm prune --omit=dev
 
-# Stage 2: Install production dependencies only
-FROM node:20-alpine AS deps
-
-WORKDIR /app
-
-RUN apk add --no-cache python3 make g++
-
-COPY package*.json ./
-RUN npm install --omit=dev
-
-# Stage 3: Runtime image
+# Stage 2: Runtime
 FROM node:20-alpine AS runtime
 
 WORKDIR /app
 
-# Data directory for SQLite database
 RUN mkdir -p /data
 
 COPY --from=builder /app/dist ./dist
-COPY --from=deps /app/node_modules ./node_modules
+COPY --from=builder /app/node_modules ./node_modules
 COPY package*.json ./
 
 ENV NODE_ENV=production