feat: implement debug logging cleanup and i18n coverage proposals

## cleanup-debug-logging
- Create environment-aware logger utility (logger.ts)
- Replace 60+ console.log/error statements across 28 files
- Production: only warn/error logs visible
- Development: all log levels with prefixes

Updated files:
- Contexts: NotificationContext, ProjectSyncContext, AuthContext
- Components: GanttChart, CalendarView, ErrorBoundary, and 11 others
- Pages: Tasks, Projects, Dashboard, and 7 others
- Services: api.ts

## complete-i18n-coverage
- WeeklyReportPreview: all strings translated, dynamic locale
- ReportHistory: all strings translated, dynamic locale
- AuditPage: detail modal and verification modal translated
- WorkloadPage: error message translated

Locale files updated:
- en/common.json, zh-TW/common.json: reports section
- en/audit.json, zh-TW/audit.json: modal sections
- en/workload.json, zh-TW/workload.json: errors section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/public/locales/zh-TW/audit.json

@@ -52,5 +52,39 @@
   "empty": {
     "title": "沒有稽核記錄",
     "description": "目前沒有符合條件的稽核記錄"
+  },
+  "modal": {
+    "details": {
+      "title": "稽核日誌詳情",
+      "eventType": "事件類型：",
+      "action": "操作：",
+      "resource": "資源：",
+      "user": "使用者：",
+      "ipAddress": "IP 位址：",
+      "sensitivity": "敏感度：",
+      "time": "時間：",
+      "changes": "變更內容",
+      "field": "欄位",
+      "oldValue": "舊值",
+      "newValue": "新值",
+      "checksum": "校驗碼：",
+      "na": "無",
+      "system": "系統"
+    },
+    "verification": {
+      "title": "完整性驗證",
+      "verifying": "正在驗證稽核日誌完整性...",
+      "verifyingHint": "根據記錄數量，這可能需要一些時間。",
+      "failed": "驗證失敗",
+      "statusSuccess": "完整性已驗證",
+      "statusFailed": "偵測到完整性問題",
+      "successDescription": "所有稽核記錄都具有有效的校驗碼，未被竄改。",
+      "failedDescription": "部分稽核記錄的校驗碼無效，表示可能存在竄改或損壞。",
+      "totalChecked": "已檢查總數",
+      "valid": "有效",
+      "invalid": "無效",
+      "invalidRecords": "無效記錄",
+      "invalidRecordsDescription": "以下記錄 ID 未通過完整性驗證："
+    }
   }
 }