feat(discovery): add FindingDrawer component and restructure i18n keys

- Add FindingDrawer component for displaying finding details when no
  associated issue exists
- Refactor i18n keys for better organization:
  - status.* → session.status.* (session-related)
  - severity.* → findings.severity.* (finding-related)
- Update DiscoveryDetail to show FindingDrawer for orphan findings
- Add severity/priority mapping in discovery-routes for compatibility

ccw/frontend/src/locales/zh/issues.json

@@ -353,7 +353,14 @@
       "hasIssue": "已关联",
       "export": "导出",
       "selectAll": "全选",
-      "deselectAll": "取消全选"
+      "deselectAll": "取消全选",
+      "description": "问题描述",
+      "location": "文件位置",
+      "codeSnippet": "代码片段",
+      "suggestedFix": "建议修复",
+      "confidence": "置信度",
+      "reference": "参考链接",
+      "perspective": "视角"
     },
     "tabs": {
       "findings": "发现",