Refactor golden image handling in backup upload process</message>

<message>Update the _set_golden_from_path function to improve the handling of existing golden image files. Replace the existing unlink logic with a more robust method that safely removes files or broken symlinks using the missing_ok parameter. This change enhances the reliability of the backup upload process by ensuring that stale references are properly cleared before setting a new golden image path.

backup-from-device/gnss-guard/tm-gnss-guard/.env.prod

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+# ============================================================================
+# GNSS Guard Configuration
+# ============================================================================
+
+# =============================================================================
+# ASSET NAME
+# =============================================================================
+ASSET_NAME=OFFICE_LAB
+
+# =============================================================================
+# DEPLOYMENT TARGET (used by deploy_client.sh)
+# =============================================================================
+DEPLOY_USER=pi
+# DEPLOY_HOST=10.130.60.253
+DEPLOY_HOST=10.15.80.161
+DEPLOY_PORT=22
+DEPLOY_PASSWORD=sh1pb0x1
+DEPLOY_INJECTED_POSITIONS=.configs/injected_positions_office_lab.json
+
+# ============================================================================
+# Timing configuration
+# ============================================================================
+ITERATION_PERIOD_SECONDS=30
+STALE_THRESHOLD_SECONDS=60
+VALIDATION_THRESHOLD_METERS=200
+STARTUP_WARMUP_SECONDS=5
+
+# ============================================================================
+# TM AIS GPS Configuration
+# ============================================================================
+TM_AIS_ENABLED=true
+TM_AIS_URL=https://localhost:8443/location
+TM_AIS_TOKEN=xuNg8eewohcieru1Noto
+TM_AIS_MAX_RETRIES=1
+
+# ============================================================================
+# Starlink Terminal Configuration
+# ============================================================================
+STARLINK_ENABLED=true
+STARLINK_IP=10.130.60.70
+STARLINK_PORT=9200
+STARLINK_MAX_RETRIES=1
+
+# ============================================================================
+# NMEA Primary Vessel GPS Configuration
+# ============================================================================
+NMEA_PRIMARY_ENABLED=true
+NMEA_PRIMARY_IP=10.130.60.61
+NMEA_PRIMARY_PORT=4001
+
+# ============================================================================
+# NMEA Secondary Vessel GPS Configuration
+# ============================================================================
+NMEA_SECONDARY_ENABLED=true
+NMEA_SECONDARY_IP=10.130.60.61
+NMEA_SECONDARY_PORT=4002
+
+# ============================================================================
+# Storage Configuration
+# ============================================================================
+DATABASE_PATH=data/gnss_guard.db
+LOGS_BASE_PATH=logs
+
+# ============================================================================
+# Web Server Configuration
+# ============================================================================
+# Enable/disable web dashboard
+WEB_ENABLED=true
+
+# Web server host (0.0.0.0 = all interfaces, 127.0.0.1 = localhost only)
+WEB_HOST=0.0.0.0
+
+# Web server port
+WEB_PORT=8080
+
+# Show 24h route on map (requires local historical data)
+WEB_SHOW_ROUTE=true
+
+# Demo mode: for demo units with pre-loaded historical data
+# When enabled:
+#   - Data collection continues normally (real or injected)
+#   - Dashboard shows live status (current validation is stored)
+#   - Recent "live" records auto-deleted to preserve historical data
+#   - NO server sync (validation not sent to cloud)
+#   - Route shows last 24h of historical data (excludes live session)
+DEMO_UNIT=true
+
+
+# Access the dashboard at:
+# - http://localhost:8080
+# - http://<server-ip>:8080
+# - http://guard.lan:8080 (if guard.lan is configured in DNS/hosts)
+
+
+# ============================================================================
+# Data Retenction Configuration
+# ============================================================================
+
+POSITIONS_RAW_RETENTION_DAYS=5
+POSITIONS_VALIDATION_RETENTION_DAYS=5
+LOG_RETENTION_DAYS=14
+
+# ============================================================================
+# Server Sync
+# ============================================================================
+
+SERVER_ENABLED=true
+SERVER_URL=https://gnss.tototheo.com
+SERVER_TOKEN=a25dee6101b944495a98f2a2c529b926ea01f36807ccb06b18240c7134ea467e
+SERVER_SYNC_BATCH_SIZE=100
+SERVER_SYNC_MAX_QUEUE=1000
+
+
+# ssh -p 22 pi@10.130.60.253
+# ssh -p 22 -L 8080:localhost:8080 pi@10.130.60.253
+
+# Download gnss_guard.db
+# scp pi@10.130.60.253:~/tm-gnss-guard/data/gnss_guard.db ./data/gnss_guard.db
+
+# Upload gnss_guard.db
+# scp ./data/gnss_guard.db pi@10.130.60.253:~/tm-gnss-guard/data/gnss_guard.db