feat(telemetry): add caching, alerts, migration & dashboard improvements

- Add Redis/in-memory caching layer (cache.go)
- Add SMTP alerting for high failure rates (alerts.go)
- Add data migration script from old API (migrate.go)
- Add docker-compose.yml for easy deployment
- Move dashboard to / with redirect from /dashboard
- Add dark/light mode toggle
- Add error analysis and failed apps statistics
- Add PVE version and LXC/VM type stats
- Add /metrics Prometheus endpoint
- Add /api/records pagination endpoint
- Add CSV export functionality
- Enhanced healthcheck with PB connection status

New ENV vars:
- Cache: ENABLE_CACHE, CACHE_TTL_SECONDS, ENABLE_REDIS, REDIS_URL
- Alerts: ALERT_ENABLED, SMTP_*, ALERT_FAILURE_THRESHOLD, etc.
- Migration: RUN_MIGRATION, MIGRATION_REQUIRED, MIGRATION_SOURCE_URL

misc/data/migrate.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+# Migration script to import data from the old API to PocketBase
+# Usage: ./migrate.sh [POCKETBASE_URL] [COLLECTION_NAME]
+#
+# Examples:
+#   ./migrate.sh                                    # Uses defaults
+#   ./migrate.sh http://localhost:8090              # Custom PB URL
+#   ./migrate.sh http://localhost:8090 my_telemetry # Custom URL and collection
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Default values
+POCKETBASE_URL="${1:-http://localhost:8090}"
+POCKETBASE_COLLECTION="${2:-_dev_telemetry_data}"
+
+echo "============================================="
+echo "   ProxmoxVED Data Migration Tool"
+echo "============================================="
+echo ""
+echo "This script will migrate telemetry data from:"
+echo "  Source: https://api.htl-braunau.at/dev/data"
+echo "  Target: $POCKETBASE_URL"
+echo "  Collection: $POCKETBASE_COLLECTION"
+echo ""
+
+# Check if PocketBase is reachable
+echo "🔍 Checking PocketBase connection..."
+if ! curl -sf "$POCKETBASE_URL/api/health" > /dev/null 2>&1; then
+    echo "❌ Cannot reach PocketBase at $POCKETBASE_URL"
+    echo "   Make sure PocketBase is running and the URL is correct."
+    exit 1
+fi
+echo "✅ PocketBase is reachable"
+echo ""
+
+# Check source API
+echo "🔍 Checking source API..."
+SUMMARY=$(curl -sf "https://api.htl-braunau.at/dev/data/summary" 2>/dev/null || echo "")
+if [ -z "$SUMMARY" ]; then
+    echo "❌ Cannot reach source API"
+    exit 1
+fi
+
+TOTAL=$(echo "$SUMMARY" | grep -o '"total_entries":[0-9]*' | cut -d: -f2)
+echo "✅ Source API is reachable ($TOTAL entries available)"
+echo ""
+
+# Confirm migration
+read -p "⚠️  Do you want to start the migration? [y/N] " -n 1 -r
+echo ""
+if [[ ! $REPLY =~ ^[Yy]$ ]]; then
+    echo "Migration cancelled."
+    exit 0
+fi
+
+echo ""
+echo "Starting migration..."
+echo ""
+
+# Run the Go migration script
+cd "$SCRIPT_DIR"
+POCKETBASE_URL="$POCKETBASE_URL" POCKETBASE_COLLECTION="$POCKETBASE_COLLECTION" go run migrate.go
+
+echo ""
+echo "Migration complete!"