Support TZ environment variable for timezone configuration

[Copilot]

The Go backend ignores the TZ environment variable. All timestamps default to UTC regardless of Docker configuration.

Changes

• Dockerfile: Install tzdata package (required on Alpine for timezone database)
• server/main.go: Read TZ environment variable at startup and set time.Local

  if tzEnv := os.Getenv("TZ"); tzEnv != "" {
      loc, err := time.LoadLocation(tzEnv)
      if err != nil {
          log.Printf("Warning: Failed to load timezone '%s': %v", tzEnv, err)
      } else {
          time.Local = loc
      }
  }

• Documentation: Add TZ environment variable usage to README and docker-compose.yml

Impact

All time.Now() calls throughout the application (backup logs, file metadata, naming rules) now respect the configured timezone instead of defaulting to UTC.

Usage:

environment:
  - TZ=Asia/Bangkok

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• go.googlesource.com
  • Triggering command: /update-job-proxy /update-job-proxy server --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-48ce6d8ec231 -j DOCKER-ISOLATION-STAGE-2 07986c7.0 git (dns block)
• google.golang.org
  • Triggering command: /update-job-proxy /update-job-proxy server --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-48ce6d8ec231 -j DOCKER-ISOLATION-STAGE-2 07986c7.0 git (dns block)
• gopkg.in
  • Triggering command: /update-job-proxy /update-job-proxy server --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-48ce6d8ec231 -j DOCKER-ISOLATION-STAGE-2 07986c7.0 git (dns block)
• gorm.io
  • Triggering command: /update-job-proxy /update-job-proxy server --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-48ce6d8ec231 -j DOCKER-ISOLATION-STAGE-2 07986c7.0 git (dns block)
• nullprogram.com
  • Triggering command: /update-job-proxy /update-job-proxy server --proxy-cert /home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt (dns block)
  • Triggering command: /update-job-proxy /update-job-proxy -o br-48ce6d8ec231 -j DOCKER-ISOLATION-STAGE-2 07986c7.0 git (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>set time zone when use docker compose</issue_title>
<issue_description>Please config to add environment for setting time zone
I use this compose file it can't change time in backend

  backapp:
    image: ghcr.io/dennis960/backapp:latest
    container_name: ${NAME:-backapp}-backapp
    restart: unless-stopped
    hostname: backapp
    environment:
      - TZ=Asia/Bangkok
    volumes:
      # custom configurations
      - backapp-data:/data
      - /etc/localtime:/etc/localtime:ro
      - /etc/timezone:/etc/timezone:ro
    networks:
      - default
    # ports:
    #   - "${PORT:-8080}:8080"

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes set time zone when use docker compose #8

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