Preliminary dockerization with scheduling (#406)

Porting working docker implementation (scheduling, etc.) into revised v2

Co-authored-by: Netsky <56271887+TheNetsky@users.noreply.github.com>

entrypoint.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Ensure Playwright uses preinstalled browsers
+export PLAYWRIGHT_BROWSERS_PATH=0
+
+# 1. Timezone: default to UTC if not provided
+: "${TZ:=UTC}"
+ln -snf "/usr/share/zoneinfo/$TZ" /etc/localtime
+echo "$TZ" > /etc/timezone
+dpkg-reconfigure -f noninteractive tzdata
+
+# 2. Validate CRON_SCHEDULE
+if [ -z "${CRON_SCHEDULE:-}" ]; then
+  echo "ERROR: CRON_SCHEDULE environment variable is not set." >&2
+  echo "Please set CRON_SCHEDULE (e.g., \"0 2 * * *\")." >&2
+  exit 1
+fi
+
+# 3. Initial run without sleep if RUN_ON_START=true
+if [ "${RUN_ON_START:-false}" = "true" ]; then
+  echo "[entrypoint] Starting initial run in background at $(date)"
+  (
+    cd /usr/src/microsoft-rewards-script || {
+      echo "[entrypoint-bg] ERROR: Unable to cd to /usr/src/microsoft-rewards-script" >&2
+      exit 1
+    }
+    # Skip random sleep for initial run, but preserve setting for cron jobs
+    SKIP_RANDOM_SLEEP=true src/run_daily.sh
+    echo "[entrypoint-bg] Initial run completed at $(date)"
+  ) &
+  echo "[entrypoint] Background process started (PID: $!)"
+fi
+
+# 4. Template and register cron file with explicit timezone export
+if [ ! -f /etc/cron.d/microsoft-rewards-cron.template ]; then
+  echo "ERROR: Cron template /etc/cron.d/microsoft-rewards-cron.template not found." >&2
+  exit 1
+fi
+
+# Export TZ for envsubst to use
+export TZ
+envsubst < /etc/cron.d/microsoft-rewards-cron.template > /etc/cron.d/microsoft-rewards-cron
+chmod 0644 /etc/cron.d/microsoft-rewards-cron
+crontab /etc/cron.d/microsoft-rewards-cron
+
+echo "[entrypoint] Cron configured with schedule: $CRON_SCHEDULE and timezone: $TZ; starting cron at $(date)"
+
+# 5. Start cron in foreground (PID 1)
+exec cron -f