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/api/hermes/model-context.ts

@@ -0,0 +1,41 @@
+import { request } from '../client'
+
+export interface ModelContext {
+  id: number
+  provider: string
+  model: string
+  context_limit: number
+}
+
+/**
+ * 根据 provider 和 model 查询模型上下文配置
+ */
+export async function getModelContext(provider: string, model: string): Promise<ModelContext | null> {
+  try {
+    const res = await request<{ data: ModelContext }>(
+      `/api/hermes/model-context?provider=${encodeURIComponent(provider)}&model=${encodeURIComponent(model)}`
+    )
+    return res.data
+  } catch (err: any) {
+    if (err.status === 404) return null
+    throw err
+  }
+}
+
+/**
+ * 设置模型上下文配置（UPSERT：存在则更新，不存在则插入）
+ */
+export async function setModelContext(
+  provider: string,
+  model: string,
+  contextLimit: number
+): Promise<ModelContext> {
+  const res = await request<{ success: boolean; data: ModelContext }>(
+    `/api/hermes/model-context/${encodeURIComponent(provider)}/${encodeURIComponent(model)}`,
+    {
+      method: 'PUT',
+      body: JSON.stringify({ provider, model, context_limit: contextLimit }),
+    }
+  )
+  return res.data
+}