Fix container timezone: set TZ=Asia/Ho_Chi_Minh (was defaulting to UTC)

Alpine base image ships no timezone data, so Date/moment() inside the
container fell back to UTC regardless of the host's real timezone -
every displayed timestamp (transaction list "Thời gian" column, CSV
export) and every signed timeStamp (epay merchantToken) was 7 hours
behind actual Vietnam time. Installs tzdata and sets TZ in both the
Dockerfile and docker-compose.yml (belt and suspenders - either alone
would fix it, but the compose env var makes it visible without having
to read the Dockerfile).

Verified by building the actual image and running new Date()/moment()
inside it: correctly shows GMT+0700 (Indochina Time) after the fix,
was UTC before.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017KPzWwuTEeX2vXGXvyGn4q

Dockerfile

 FROM node:20-alpine
 
+# Alpine images have no timezone data by default - without this, Date/moment()
+# fall back to UTC inside the container regardless of the host's real timezone,
+# which showed up as every displayed/signed timestamp being 7 hours behind
+# actual Vietnam time (UTC+7, no DST).
+RUN apk add --no-cache tzdata
+ENV TZ=Asia/Ho_Chi_Minh
+
 WORKDIR /app
 
 # Install dependencies first so this layer is cached unless package*.json changes.

docker-compose.yml

@@ -7,6 +7,7 @@ services:
       NODE_ENV: production
       REDIS_HOST: redis
       REDIS_PORT: 6379
+      TZ: Asia/Ho_Chi_Minh
     ports:
       # Host port 7003 chosen because this VPS is shared with many other
       # services; 3003 (and most of the 3000-3003/8080-8090/9000-9080 range)