refactor(codex): remove configuration wizard and unify provider setup experience

- Remove CodexQuickWizardModal component (~300 lines)
- Add "Custom (Blank Template)" preset with annotated TOML template
- Unify configuration experience across Claude/Codex/Gemini
- Remove wizard-related i18n keys, keep apiUrlLabel for CodexFormFields
- Simplify component integration by removing wizard state management

This change reduces code complexity by ~250 lines while providing better
user education through commented configuration templates in Chinese.

Users can now:
1. Select "Custom (Blank Template)" preset
2. See annotated TOML template with inline documentation
3. Follow step-by-step comments to configure custom providers

BREAKING CHANGE: Configuration wizard UI removed, replaced with template-based approach

src/config/codexProviderPresets.ts

@@ -98,6 +98,52 @@ requires_openai_auth = true`,
       textColor: "#FFFFFF",
     },
   },
+  {
+    name: "Custom (Blank Template)",
+    websiteUrl: "https://docs.anthropic.com",
+    category: "third_party",
+    isCustomTemplate: true,
+    auth: generateThirdPartyAuth(""),
+    config: `# ========================================
+# Codex 自定义供应商配置模板
+# ========================================
+# 快速上手：
+# 1. 在上方 auth.json 中设置 API Key
+# 2. 将下方 'custom' 替换为供应商名称（小写、无空格）
+# 3. 替换 base_url 为实际的 API 端点
+# 4. 根据需要调整模型名称
+#
+# 文档: https://docs.anthropic.com
+# ========================================
+
+# ========== 模型配置 ==========
+model_provider = "custom"        # 供应商唯一标识
+model = "gpt-5-codex"            # 模型名称
+model_reasoning_effort = "high"  # 推理强度：low, medium, high
+disable_response_storage = true  # 隐私：不本地存储响应
+
+# ========== 供应商设置 ==========
+[model_providers.custom]
+name = "custom"                                    # 与上方 model_provider 保持一致
+base_url = "https://api.example.com/v1"           # 👈 替换为实际端点
+wire_api = "responses"                            # API 响应格式
+requires_openai_auth = true                       # 使用 auth.json 中的 OPENAI_API_KEY
+
+# ========== 可选：自定义请求头 ==========
+# 如果供应商需要自定义请求头，取消注释：
+# [model_providers.custom.headers]
+# X-Custom-Header = "value"
+
+# ========== 可选：模型覆盖 ==========
+# 如果需要覆盖特定模型，取消注释：
+# [model_overrides]
+# "gpt-5-codex" = { model_provider = "custom", model = "your-model-name" }`,
+    theme: {
+      icon: "generic",
+      backgroundColor: "#6B7280", // gray-500
+      textColor: "#FFFFFF",
+    },
+  },
   {
     name: "AiHubMix",
     websiteUrl: "https://aihubmix.com",