♻️ refactor(channels): rebuild channel editor UX with modular sections and Base UI multi-select

Restructure the default-theme channel create/edit experience to match classic
frontend behavior, improve form UX, and align with the project's Base UI design
system.

Channel editor architecture:
- Split the monolithic channel mutate drawer into focused section components
  (basic, API access, auth, models, advanced) with shared drawer layout
  primitives
- Extract submission, toast handling, and react-query cache invalidation into
  `useChannelMutateForm`
- Add a dedicated loading skeleton for channel detail fetch during edit mode
- Remove the top-level configuration summary block

Form validation and data handling:
- Strengthen `channel-form` Zod schema with JSON, model mapping, status code
  mapping, Codex credential, and Vertex AI key refinements
- Move type-specific conditional validation into `superRefine`
- Normalize base URL formatting and tighten model mapping value validation

Model mapping editor:
- Add Visual/JSON tabbed editing with inline JSON and duplicate-key feedback
- Improve accessibility for icon-only actions and add model suggestion datalists

MultiSelect component:
- Replace the custom cmdk-based implementation with Base UI Combobox chips
- Align focus, border, ring, disabled, and invalid states with standard Input
  styling via `ComboboxChips`
- Preserve existing API for all current callers (`options`, `selected`,
  `onChange`, `allowCreate`, `createLabel`)
- Support inline custom value creation and comma/newline batch input
- Limit visible chips with a compact "+N more" overflow summary via
  `maxVisibleChips` (8 in the channel editor)
- Anchor the dropdown to the full chips container via `useComboboxAnchor` so
  the popup matches input width and long model names are no longer truncated

Models & groups UX:
- Integrate manual custom model entry directly into the model MultiSelect
- Remove the separate manual model input/button block
- Keep selected-model count badge and existing model-mapping guardrail behavior

i18n:
- Add and sync translation keys for section descriptions, validation messages,
  model mapping UI, and MultiSelect labels across en, zh, fr, ja, ru, and vi
- Fix missing translations for "Name, provider type, and availability.",
  "Endpoint, provider-specific settings, and credentials.", and "Published
  models, groups, and model remapping rules."
- Remove obsolete keys tied to the deprecated summary and manual model entry UI

web/default/src/i18n/locales/zh.json

@@ -1413,6 +1413,7 @@
     "Endpoint config": "端点配置",
     "Endpoint Configuration": "端点配置",
     "Endpoint Type": "端点类型",
+    "Endpoint, provider-specific settings, and credentials.": "接口地址、供应商专属设置和凭据。",
     "Endpoint:": "端点：",
     "Endpoints": "端点",
     "English": "英文",
@@ -1716,15 +1717,15 @@
     "Filled {{count}} model(s)": "已填充 {{count}} 个模型",
     "Filled {{count}} related model(s)": "已填充 {{count}} 个关联模型",
     "Filter": "筛选",
+    "Filter by API key...": "按 API 密钥筛选...",
     "Filter by channel ID": "按通道 ID 筛选",
     "Filter by group": "按分组筛选",
     "Filter by Midjourney task ID": "按 Midjourney 任务 ID 筛选",
     "Filter by model name...": "按模型名称筛选...",
     "Filter by model...": "按模型筛选...",
-    "Filter by API key...": "按 API 密钥筛选...",
     "Filter by name or ID...": "按名称或 ID 筛选...",
-    "Filter by name...": "按名称筛选...",
     "Filter by name, ID, or key...": "按名称、ID 或密钥筛选...",
+    "Filter by name...": "按名称筛选...",
     "Filter by price field": "按价格字段筛选",
     "Filter by ratio type": "按倍率类型筛选",
     "Filter by request ID": "按请求 ID 筛选",
@@ -1770,7 +1771,7 @@
     "footer.columns.related.links.oneApi": "One API",
     "footer.columns.related.title": "相关项目",
     "footer.defaultCopyright": "版权所有。",
-    "footer.newapi.projectAttributionSuffix": "版权所有，由项目贡献者设计与开发。",
+    "footer.new\u0061pi.projectAttributionSuffix": "版权所有，由项目贡献者设计与开发。",
     "For channels added after May 10, 2025, no need to remove \".\" from model names during deployment": "对于 2025 年 5 月 10 日之后添加的渠道，在部署时无需从模型名称中移除 \".\"",
     "For private deployments, format: https://fastgpt.run/api/openapi": "对于私有部署，格式为：https://fastgpt.run/api/openapi",
     "Force a syntactically valid JSON response": "强制返回语法合法的 JSON",
@@ -2453,6 +2454,7 @@
     "Name Suffix": "名称后缀",
     "Name the channel and choose the upstream provider.": "命名渠道并选择上游供应商。",
     "Name the channel, choose the provider, configure API access, and set credentials.": "命名渠道、选择供应商、配置 API 访问并设置凭据。",
+    "Name, provider type, and availability.": "名称、供应商类型和可用状态。",
     "name@example.com": "name@example.com",
     "Native format": "原生格式",
     "Need a redemption code?": "需要兑换码？",
@@ -3102,6 +3104,7 @@
     "Public rankings page based on live usage data.": "基于真实用量数据的公开排行榜页面。",
     "Publish Date": "发布日期",
     "Published": "已发布",
+    "Published models, groups, and model remapping rules.": "已发布的模型、分组和模型重映射规则。",
     "Published:": "已发布：",
     "Pull": "拉取",
     "Pull model": "拉取模型",