[fix] Droid: dynamic x-api-provider and custom User-Agent support

- Dynamic x-api-provider selection for OpenAI endpoint based on model
  - Models with '-max' suffix use 'openai' provider
  - Other models use 'azure_openai' provider
  - Fixes gpt-5.1-codex-max model compatibility issue

- Update default User-Agent to factory-cli/0.32.1

- Add custom User-Agent field for Droid accounts
  - Backend: userAgent field in createAccount and updateAccount
  - Frontend: User-Agent input in account creation/edit UI
  - Supports all Droid auth modes: OAuth, Manual, API Key

This resolves the issue where gpt-5.1-codex-max failed with 'Azure OpenAI only supports...' error due to incorrect provider header.

src/services/droidAccountService.js

@@ -556,7 +556,8 @@ class DroidAccountService {
       tokenType = 'Bearer',
       authenticationMethod = '',
       expiresIn = null,
-      apiKeys = []
+      apiKeys = [],
+      userAgent = ''  // 自定义 User-Agent
     } = options
 
     const accountId = uuidv4()
@@ -832,7 +833,8 @@ class DroidAccountService {
           : '',
       apiKeys: hasApiKeys ? JSON.stringify(apiKeyEntries) : '',
       apiKeyCount: hasApiKeys ? String(apiKeyEntries.length) : '0',
-      apiKeyStrategy: hasApiKeys ? 'random_sticky' : ''
+      apiKeyStrategy: hasApiKeys ? 'random_sticky' : '',
+      userAgent: userAgent || ''  // 自定义 User-Agent
     }
 
     await redis.setDroidAccount(accountId, accountData)
@@ -931,6 +933,11 @@ class DroidAccountService {
       sanitizedUpdates.endpointType = this._sanitizeEndpointType(sanitizedUpdates.endpointType)
     }
 
+    // 处理 userAgent 字段
+    if (typeof sanitizedUpdates.userAgent === 'string') {
+      sanitizedUpdates.userAgent = sanitizedUpdates.userAgent.trim()
+    }
+
     const parseProxyConfig = (value) => {
       if (!value) {
         return null