Refactor UI/views, rework Docker build, untrack local data

- Views umstrukturiert: einstellungen.ejs -> bewerbung.ejs, neues
  partials/head.ejs, header/footer/index angepasst
- CSS umbenannt: style.css -> styles.css
- server.js und public/js/main.js ueberarbeitet
- Dockerfile auf schlankes Multi-Stage-Setup umgestellt;
  docker-compose.yml und .dockerignore entfernt
- npm-Scripts docker:build/push/deploy ergaenzt
- SQLite-DB und .idea aus Git entfernt und via .gitignore ignoriert

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Dockerfile

@@ -1,35 +1,45 @@
-# ── Stage 1: Dependencies (mit Compiler für better-sqlite3) ──────────────────
-FROM node:20.19.2-slim AS deps
+# syntax=docker/dockerfile:1
+
+# ----- Build stage: install (and compile native sqlite3) deps -----
+FROM node:20-bookworm-slim AS builder
 
 WORKDIR /app
 
-RUN apt-get update && apt-get install -y --no-install-recommends \
-        python3 make g++ \
+# Build toolchain required to compile the native sqlite3 binding
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends python3 make g++ \
     && rm -rf /var/lib/apt/lists/*
 
+# Install production dependencies deterministically (cached unless lockfile changes)
 COPY package.json package-lock.json ./
 RUN npm ci --omit=dev
 
-# ── Stage 2: Runtime ──────────────────────────────────────────────────────────
-FROM node:20.19.2-slim AS runtime
+# ----- Runtime stage: slim image without build tooling -----
+FROM node:20-bookworm-slim AS runtime
+
+ENV NODE_ENV=production \
+    PORT=3000
 
 WORKDIR /app
 
-RUN groupadd --system --gid 1001 nodejs \
-    && useradd --system --uid 1001 --gid nodejs --no-create-home appuser
+# Bring in the already-installed (and compiled) dependencies
+COPY --from=builder /app/node_modules ./node_modules
 
-COPY --from=deps /app/node_modules ./node_modules
-COPY . .
-
-RUN mkdir -p data && chown -R appuser:nodejs data
+# Application source
+COPY package.json ./
+COPY server.js ./
+COPY views ./views
+COPY public ./public
 
+# Persisted SQLite data lives here; make it writable for the non-root user
+RUN mkdir -p /app/data && chown -R node:node /app
 VOLUME ["/app/data"]
 
-USER appuser
+USER node
 
 EXPOSE 3000
 
 HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
-    CMD node -e "require('http').get('http://localhost:3000/',r=>process.exit(r.statusCode===200?0:1)).on('error',()=>process.exit(1))"
+    CMD node -e "fetch('http://localhost:'+(process.env.PORT||3000)+'/').then(r=>process.exit(r.ok?0:1)).catch(()=>process.exit(1))"
 
 CMD ["node", "server.js"]