feat(logging): add Seq transport, global meta fields, and improve error handling

- Add Seq centralized logging transport with async ESM import
- Add appVersion and computerName to logger defaultMeta (all app logs)
- Add appVersion to audit log entries for version-level traceability
- Improve unhandledRejection to capture full stack traces for Error instances
- Add Seq config schema and template configuration

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

src/main/services/logger/seq-transport.ts

@@ -0,0 +1,131 @@
+/**
+ * Seq logging transport using @datalust/winston-seq
+ *
+ * Provides asynchronous batched logging to Seq server
+ * with configurable parameters for production use.
+ *
+ * Features:
+ * - Non-blocking async batch sending (via dynamic import)
+ * - Configurable batch size, period, queue limits
+ * - Automatic retry on failure
+ * - Graceful shutdown with flush
+ * - Error suppression (Seq failures don't crash app)
+ *
+ * Note: Uses dynamic import because @datalust/winston-seq is an ESM module
+ */
+
+import type { SeqConfig } from '../../types/config.schema'
+import logger from './index'
+
+/**
+ * Seq transport constructor type (from dynamic import)
+ */
+type SeqTransportClass = new (options: {
+  serverUrl: string
+  apiKey?: string
+  batchSizeLimit?: number
+  maxBatchingTime?: number
+  maxRetries?: number
+  onError?: (error: Error) => void
+}) => any
+
+/**
+ * Create and configure Seq transport dynamically
+ *
+ * This function handles the ESM module loading and returns
+ * a configured transport instance compatible with Winston.
+ *
+ * @param config - Seq configuration from config.schema
+ * @returns Promise resolving to transport instance or null if disabled/failed
+ */
+export async function createSeqTransport(config: SeqConfig): Promise<any> {
+  // Don't create transport if disabled
+  if (!config.enabled || !config.serverUrl) {
+    logger.info('Seq logging is disabled or server URL not provided', {
+      enabled: config.enabled,
+      hasServerUrl: !!config.serverUrl,
+      context: 'seq-transport'
+    })
+    return null
+  }
+
+  try {
+    // Dynamically import the ESM module
+    const { SeqTransport } = await import('@datalust/winston-seq')
+    const SeqTransportClass = SeqTransport as SeqTransportClass
+
+    // Create transport instance with mapped config
+    const transport = new SeqTransportClass({
+      serverUrl: config.serverUrl,
+      apiKey: config.apiKey || undefined,
+      batchSizeLimit: config.batchPostingLimit,
+      maxBatchingTime: config.period,
+      maxRetries: config.maxRetries,
+      onError: (error: Error) => {
+        // Log errors but don't throw - Seq failures should not crash app
+        logger.error('Seq transport error', {
+          error: error.message,
+          stack: error.stack,
+          context: 'seq-transport'
+        })
+      }
+    })
+
+    logger.info('Seq transport created successfully', {
+      serverUrl: config.serverUrl,
+      batchPostingLimit: config.batchPostingLimit,
+      period: config.period,
+      maxRetries: config.maxRetries,
+      context: 'seq-transport'
+    })
+
+    return transport
+  } catch (error) {
+    logger.error('Failed to create Seq transport', {
+      error: error instanceof Error ? error.message : String(error),
+      context: 'seq-transport'
+    })
+    // Return null to allow app to continue without Seq
+    return null
+  }
+}
+
+/**
+ * Sync factory wrapper for backward compatibility
+ *
+ * Note: This creates the transport asynchronously internally.
+ * The transport is cached and reused.
+ */
+let cachedTransport: any = null
+let isInitializing = false
+
+export function createSeqTransportSync(config: SeqConfig): any {
+  if (!config.enabled || !config.serverUrl) {
+    return null
+  }
+
+  if (cachedTransport) {
+    return cachedTransport
+  }
+
+  if (!isInitializing) {
+    isInitializing = true
+    createSeqTransport(config)
+      .then((transport) => {
+        cachedTransport = transport
+      })
+      .catch((error) => {
+        logger.error('Seq transport initialization failed', {
+          error: error instanceof Error ? error.message : String(error)
+        })
+      })
+      .finally(() => {
+        isInitializing = false
+      })
+  }
+
+  // Return null on first call, transport will be available on next call
+  return null
+}
+
+export default createSeqTransportSync