refactor: split ProviderForm into smaller focused components

- Created ProviderPresetSelector component (80 lines)
- Created BasicFormFields component (60 lines)
- Created ClaudeFormFields component (272 lines)
- Created CodexFormFields component (131 lines)
- Reduced ProviderForm from 866 to 544 lines (37% reduction)

Each component now has a clear single responsibility:
- ProviderPresetSelector: Handles preset selection UI
- BasicFormFields: Name and website URL inputs
- ClaudeFormFields: All Claude-specific form fields
- CodexFormFields: All Codex-specific form fields
- ProviderForm: Orchestrates hooks and component composition

Benefits:
- Better code organization and maintainability
- Easier to test individual components
- Clearer separation of concerns
- More reusable components

src/components/providers/forms/CodexFormFields.tsx

@@ -0,0 +1,131 @@
+import { useTranslation } from "react-i18next";
+import { FormLabel } from "@/components/ui/form";
+import { Input } from "@/components/ui/input";
+import ApiKeyInput from "@/components/ProviderForm/ApiKeyInput";
+import EndpointSpeedTest from "@/components/ProviderForm/EndpointSpeedTest";
+import { Zap } from "lucide-react";
+import type { ProviderCategory } from "@/types";
+
+interface CodexFormFieldsProps {
+  // API Key
+  codexApiKey: string;
+  onApiKeyChange: (key: string) => void;
+  category?: ProviderCategory;
+  shouldShowApiKeyLink: boolean;
+  websiteUrl: string;
+
+  // Base URL
+  shouldShowSpeedTest: boolean;
+  codexBaseUrl: string;
+  onBaseUrlChange: (url: string) => void;
+  isEndpointModalOpen: boolean;
+  onEndpointModalToggle: (open: boolean) => void;
+  onCustomEndpointsChange: (endpoints: string[]) => void;
+}
+
+export function CodexFormFields({
+  codexApiKey,
+  onApiKeyChange,
+  category,
+  shouldShowApiKeyLink,
+  websiteUrl,
+  shouldShowSpeedTest,
+  codexBaseUrl,
+  onBaseUrlChange,
+  isEndpointModalOpen,
+  onEndpointModalToggle,
+  onCustomEndpointsChange,
+}: CodexFormFieldsProps) {
+  const { t } = useTranslation();
+
+  return (
+    <>
+      {/* Codex API Key 输入框 */}
+      <div className="space-y-1">
+        <ApiKeyInput
+          id="codexApiKey"
+          label="API Key"
+          value={codexApiKey}
+          onChange={onApiKeyChange}
+          required={category !== "official"}
+          placeholder={
+            category === "official"
+              ? t("providerForm.codexOfficialNoApiKey", {
+                  defaultValue: "官方供应商无需 API Key",
+                })
+              : t("providerForm.codexApiKeyAutoFill", {
+                  defaultValue: "输入 API Key，将自动填充到配置",
+                })
+          }
+          disabled={category === "official"}
+        />
+        {/* Codex API Key 获取链接 */}
+        {shouldShowApiKeyLink && websiteUrl && (
+          <div className="-mt-1 pl-1">
+            <a
+              href={websiteUrl}
+              target="_blank"
+              rel="noopener noreferrer"
+              className="text-xs text-blue-400 dark:text-blue-500 hover:text-blue-500 dark:hover:text-blue-400 transition-colors"
+            >
+              {t("providerForm.getApiKey", {
+                defaultValue: "获取 API Key",
+              })}
+            </a>
+          </div>
+        )}
+      </div>
+
+      {/* Codex Base URL 输入框 */}
+      {shouldShowSpeedTest && (
+        <div className="space-y-2">
+          <div className="flex items-center justify-between">
+            <FormLabel htmlFor="codexBaseUrl">
+              {t("codexConfig.apiUrlLabel", { defaultValue: "API 端点" })}
+            </FormLabel>
+            <button
+              type="button"
+              onClick={() => onEndpointModalToggle(true)}
+              className="flex items-center gap-1 text-xs text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-gray-100 transition-colors"
+            >
+              <Zap className="h-3.5 w-3.5" />
+              {t("providerForm.manageAndTest", {
+                defaultValue: "管理和测速",
+              })}
+            </button>
+          </div>
+          <Input
+            id="codexBaseUrl"
+            type="url"
+            value={codexBaseUrl}
+            onChange={(e) => onBaseUrlChange(e.target.value)}
+            placeholder={t("providerForm.codexApiEndpointPlaceholder", {
+              defaultValue: "https://api.example.com/v1",
+            })}
+            autoComplete="off"
+          />
+          <div className="p-3 bg-amber-50 dark:bg-amber-900/20 border border-amber-200 dark:border-amber-700 rounded-lg">
+            <p className="text-xs text-amber-600 dark:text-amber-400">
+              {t("providerForm.codexApiHint", {
+                defaultValue: "Codex API 端点地址",
+              })}
+            </p>
+          </div>
+        </div>
+      )}
+
+      {/* 端点测速弹窗 - Codex */}
+      {shouldShowSpeedTest && isEndpointModalOpen && (
+        <EndpointSpeedTest
+          appType="codex"
+          value={codexBaseUrl}
+          onChange={onBaseUrlChange}
+          initialEndpoints={[{ url: codexBaseUrl }]}
+          visible={isEndpointModalOpen}
+          onClose={() => onEndpointModalToggle(false)}
+          onCustomEndpointsChange={onCustomEndpointsChange}
+        />
+      )}
+    </>
+  );
+}