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/entrypoint.sh

@@ -0,0 +1,50 @@
+#!/bin/sh
+set -e
+
+echo "============================================="
+echo "   ProxmoxVED Telemetry Service"
+echo "============================================="
+
+# Run migration if enabled
+if [ "$RUN_MIGRATION" = "true" ]; then
+    echo ""
+    echo "🔄 Migration mode enabled"
+    echo "   Source: $MIGRATION_SOURCE_URL"
+    echo "   Target: $POCKETBASE_URL"
+    echo "   Collection: $POCKETBASE_COLLECTION"
+    echo ""
+    
+    # Wait for PocketBase to be ready
+    echo "⏳ Waiting for PocketBase to be ready..."
+    RETRIES=30
+    until wget -q --spider "$POCKETBASE_URL/api/health" 2>/dev/null; do
+        RETRIES=$((RETRIES - 1))
+        if [ $RETRIES -le 0 ]; then
+            echo "❌ PocketBase not reachable after 30 attempts"
+            if [ "$MIGRATION_REQUIRED" = "true" ]; then
+                exit 1
+            fi
+            echo "⚠️  Continuing without migration..."
+            break
+        fi
+        echo "   Waiting... ($RETRIES attempts left)"
+        sleep 2
+    done
+    
+    if wget -q --spider "$POCKETBASE_URL/api/health" 2>/dev/null; then
+        echo "✅ PocketBase is ready"
+        echo ""
+        echo "🚀 Starting migration..."
+        /app/migrate || {
+            if [ "$MIGRATION_REQUIRED" = "true" ]; then
+                echo "❌ Migration failed!"
+                exit 1
+            fi
+            echo "⚠️  Migration failed, but continuing..."
+        }
+        echo ""
+    fi
+fi
+
+echo "🚀 Starting telemetry service..."
+exec /app/telemetry-ingest