refactor: remove per-provider proxy config feature

The per-provider proxy configuration (meta.proxyConfig) is removed
because its scope is too narrow and covered by global proxy settings
and proxy takeover mode. Users can achieve the same result via the
global proxy panel.

Changes:
- Remove ProviderProxyConfig type (frontend TS + backend Rust)
- Remove ProviderAdvancedConfig proxy UI block, keep testConfig/pricingConfig
- Simplify http_client: delete build_proxy_url_from_config,
  build_client_for_provider, get_for_provider
- Simplify forwarder/stream_check/model_fetch to use global client
- Remove i18n keys (en/zh/ja)
- Fix pre-existing test bug in transform.rs (extra None arg)

src-tauri/src/proxy/forwarder.rs

@@ -1347,12 +1347,8 @@ impl RequestForwarder {
             self.non_streaming_timeout
         };
 
-        // 解析上游代理 URL（供应商单独代理 > 全局代理 > 无）
-        let proxy_config = provider.meta.as_ref().and_then(|m| m.proxy_config.as_ref());
-        let upstream_proxy_url: Option<String> = proxy_config
-            .filter(|c| c.enabled)
-            .and_then(super::http_client::build_proxy_url_from_config)
-            .or_else(super::http_client::get_current_proxy_url);
+        // 获取全局代理 URL
+        let upstream_proxy_url: Option<String> = super::http_client::get_current_proxy_url();
 
         // SOCKS5 代理不支持 CONNECT 隧道，需要用 reqwest
         let is_socks_proxy = upstream_proxy_url
@@ -1368,7 +1364,7 @@ impl RequestForwarder {
         let response = if is_socks_proxy {
             // SOCKS5 代理：只能走 reqwest（不支持 header case 保留）
             log::debug!("[Forwarder] Using reqwest for SOCKS5 proxy");
-            let client = super::http_client::get_for_provider(proxy_config);
+            let client = super::http_client::get();
             let mut request = client.post(&url);
             if !self.non_streaming_timeout.is_zero() {
                 request = request.timeout(self.non_streaming_timeout);

src-tauri/src/proxy/http_client.rs

@@ -3,7 +3,6 @@
 //! 提供支持全局代理配置的 HTTP 客户端。
 //! 所有需要发送 HTTP 请求的模块都应使用此模块提供的客户端。
 
-use crate::provider::ProviderProxyConfig;
 use once_cell::sync::OnceCell;
 use reqwest::Client;
 use std::env;
@@ -334,103 +333,6 @@ pub fn mask_url(url: &str) -> String {
     }
 }
 
-/// 根据供应商单独代理配置构建代理 URL
-///
-/// 将 ProviderProxyConfig 转换为代理 URL 字符串
-pub fn build_proxy_url_from_config(config: &ProviderProxyConfig) -> Option<String> {
-    let proxy_type = config.proxy_type.as_deref().unwrap_or("http");
-    let host = config.proxy_host.as_deref()?;
-    let port = config.proxy_port?;
-
-    // 构建带认证的代理 URL
-    if let (Some(username), Some(password)) = (&config.proxy_username, &config.proxy_password) {
-        if !username.is_empty() && !password.is_empty() {
-            return Some(format!(
-                "{proxy_type}://{username}:{password}@{host}:{port}"
-            ));
-        }
-    }
-
-    Some(format!("{proxy_type}://{host}:{port}"))
-}
-
-/// 根据供应商单独代理配置构建 HTTP 客户端
-///
-/// 如果供应商配置了单独代理（enabled = true），则使用该代理构建客户端；
-/// 否则返回 None，调用方应使用全局客户端。
-///
-/// # Arguments
-/// * `proxy_config` - 供应商的代理配置
-///
-/// # Returns
-/// 如果配置有效则返回 Some(Client)，否则返回 None
-pub fn build_client_for_provider(proxy_config: Option<&ProviderProxyConfig>) -> Option<Client> {
-    let config = proxy_config.filter(|c| c.enabled)?;
-
-    let proxy_url = build_proxy_url_from_config(config)?;
-
-    log::debug!(
-        "[ProviderProxy] Building client with proxy: {}",
-        mask_url(&proxy_url)
-    );
-
-    // 构建带代理的客户端
-    let proxy = match reqwest::Proxy::all(&proxy_url) {
-        Ok(p) => p,
-        Err(e) => {
-            log::error!(
-                "[ProviderProxy] Failed to create proxy from '{}': {}",
-                mask_url(&proxy_url),
-                e
-            );
-            return None;
-        }
-    };
-
-    match Client::builder()
-        .timeout(Duration::from_secs(600))
-        .connect_timeout(Duration::from_secs(30))
-        .pool_max_idle_per_host(10)
-        .tcp_keepalive(Duration::from_secs(60))
-        .no_gzip()
-        .no_brotli()
-        .no_deflate()
-        .proxy(proxy)
-        .build()
-    {
-        Ok(client) => {
-            log::info!(
-                "[ProviderProxy] Client built with proxy: {}",
-                mask_url(&proxy_url)
-            );
-            Some(client)
-        }
-        Err(e) => {
-            log::error!("[ProviderProxy] Failed to build client: {e}");
-            None
-        }
-    }
-}
-
-/// 获取供应商专用的 HTTP 客户端
-///
-/// 优先使用供应商单独代理配置，如果未启用则返回全局客户端。
-///
-/// # Arguments
-/// * `proxy_config` - 供应商的代理配置
-///
-/// # Returns
-/// 返回适合该供应商的 HTTP 客户端
-pub fn get_for_provider(proxy_config: Option<&ProviderProxyConfig>) -> Client {
-    // 优先使用供应商单独代理
-    if let Some(client) = build_client_for_provider(proxy_config) {
-        return client;
-    }
-
-    // 回退到全局客户端
-    get()
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src-tauri/src/proxy/providers/transform.rs

@@ -661,7 +661,7 @@ mod tests {
             "messages": [{"role": "user", "content": "Hello"}]
         });
 
-        let result = anthropic_to_openai(input, None).unwrap();
+        let result = anthropic_to_openai(input).unwrap();
         assert_eq!(result["messages"][0]["role"], "system");
         assert_eq!(
             result["messages"][0]["content"],
@@ -682,7 +682,7 @@ mod tests {
             "messages": [{"role": "user", "content": "Hello"}]
         });
 
-        let result = anthropic_to_openai(input, None).unwrap();
+        let result = anthropic_to_openai(input).unwrap();
         assert_eq!(result["messages"][0]["role"], "system");
         assert_eq!(
             result["messages"][0]["content"],