Enhance Dockerfile and Redis configuration for improved build-time handling

- Added environment variables in Dockerfile for build-time placeholders, ensuring proper static analysis during the build process.
- Updated Redis initialization in redis.ts to include lazy connection, preventing network access during module import and improving error handling with a console log for connection errors.

apps/webui/Dockerfile

@@ -17,6 +17,25 @@ COPY eslint.config.js .eslintrc.cjs .prettierrc ./
 RUN pnpm install --frozen-lockfile=false
 RUN pnpm --filter @nexumi/shared build
 RUN pnpm --filter @nexumi/webui prisma:generate
+# `next build` statically evaluates route/module code while collecting page
+# data. Our env schema and Prisma client are validated eagerly at import
+# time, so the build needs *some* well-formed values even though no real
+# secrets or network access are available at build time. These placeholders
+# are only used for that static analysis step and are always overridden by
+# the real values from `.env` (via docker-compose `env_file`) at container
+# start, since this ENV only applies to this intermediate build stage and is
+# never copied into the `runner` stage / final image.
+# Note: this intentionally triggers a "SecretsUsedInArgOrEnv" lint warning
+# because of the variable names — the values below are non-sensitive
+# placeholders, not real secrets.
+ENV NODE_ENV=production \
+    DATABASE_URL=postgresql://build:build@localhost:5432/build \
+    REDIS_URL=redis://localhost:6379 \
+    BOT_CLIENT_ID=0000000000000000000 \
+    BOT_CLIENT_SECRET=build-time-placeholder \
+    WEBUI_URL=http://localhost:3000 \
+    SESSION_SECRET=build-time-placeholder-session-secret-32chars \
+    DEFAULT_LOCALE=de
 RUN pnpm --filter @nexumi/webui build
 
 FROM base AS runner

apps/webui/src/lib/redis.ts

@@ -3,8 +3,19 @@ import { env } from './env';
 
 const globalForRedis = globalThis as unknown as { __nexumiRedis?: Redis };
 
-export const redis: Redis = globalForRedis.__nexumiRedis ?? new Redis(env.REDIS_URL, {
-  maxRetriesPerRequest: 3
+export const redis: Redis =
+  globalForRedis.__nexumiRedis ??
+  new Redis(env.REDIS_URL, {
+    maxRetriesPerRequest: 3,
+    // Defer the actual TCP connection until the first command is issued.
+    // This keeps module import side-effect free, which matters for
+    // Next.js's build-time "collect page data" step (no network access
+    // there) and avoids unhandled 'error' events on unreachable hosts.
+    lazyConnect: true
+  });
+
+redis.on('error', (error) => {
+  console.error('[redis]', error.message);
 });
 
 if (env.NODE_ENV !== 'production') {