feat: Add database table for model context length configuration (#477)

* feat: add database table for model context length configuration

- Add model_context table with provider/model/context_limit fields
- Implement UPSERT endpoint for model context configuration
- Add priority lookup: database > config.yaml > custom_providers > cache
- Add frontend click-to-edit UI in ChatInput with tooltip
- Add i18n support for context editing dialog (all 8 locales)
- Use context_limit field consistently across frontend and backend

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

* fix: use useMessage() composable instead of window.$message in ChatInput

- Remove incorrect NMessage import (not a component)
- Use useMessage() composable from naive-ui
- Replace window.$message?.xxx() with message.xxx()
- Fixes TypeScript build errors

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

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/client/src/i18n/locales/ko.ts

@@ -104,6 +104,16 @@ export default {
   // 채팅
   chat: {
     contextRemaining: '남음',
+    contextClickToEdit: '클릭하여 컨텍스트 길이 편집',
+    contextEditTitle: '컨텍스트 길이 편집',
+    contextEditDesc: '현재 모델의 컨텍스트 길이 제한 설정 (토큰 수)',
+    contextEditPlaceholder: '컨텍스트 길이 입력',
+    contextEditHint: '일반적인 값: 200k (Claude), 128k (GPT-4), 32k (GPT-3.5)',
+    contextEditSave: '저장',
+    contextEditCancel: '취소',
+    contextEditInvalid: '유효한 컨텍스트 길이를 입력하세요',
+    contextEditSuccess: '컨텍스트 길이가 업데이트되었습니다',
+    contextEditFailed: '업데이트 실패',
     emptyState: 'Hermes Agent와 대화를 시작하세요',
     inputPlaceholder: '메시지를 입력하세요... (Enter로 전송, Shift+Enter로 줄바꿈)',
     attachFiles: '파일 첨부',