feat: landing zone backup to R2 via rclone + Litestream

Landing files (append-only JSON.gz) synced to R2 every 30 min via
systemd timer + rclone. Extraction state DB (.state.sqlite) continuously
replicated via Litestream (second DB entry). Auto-restore on container
startup for both app.db and .state.sqlite. Reuses existing R2 bucket
and credentials — no new env vars needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infra/landing-backup/padelnomics-landing-backup.service

@@ -0,0 +1,20 @@
+[Unit]
+Description=Padelnomics Landing Zone Backup to R2
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+EnvironmentFile=/opt/padelnomics/.env
+Environment=LANDING_DIR=/data/padelnomics/landing
+ExecStart=/usr/bin/rclone sync ${LANDING_DIR} :s3:${LITESTREAM_R2_BUCKET}/padelnomics/landing \
+    --s3-provider Cloudflare \
+    --s3-access-key-id ${LITESTREAM_R2_ACCESS_KEY_ID} \
+    --s3-secret-access-key ${LITESTREAM_R2_SECRET_ACCESS_KEY} \
+    --s3-endpoint https://${LITESTREAM_R2_ENDPOINT} \
+    --s3-no-check-bucket \
+    --exclude ".state.sqlite*"
+
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=padelnomics-landing-backup

infra/landing-backup/padelnomics-landing-backup.timer

@@ -0,0 +1,9 @@
+[Unit]
+Description=Sync landing zone to R2 every 30 minutes
+
+[Timer]
+OnBootSec=5min
+OnUnitActiveSec=30min
+
+[Install]
+WantedBy=timers.target