[GUI] 多处错误处理静默吞异常无用户反馈

[TrueNine]

Bug Description

多处使用 .catch(() => {}) 或 catch { /* ignore */ } 静默吞掉异常。例如 PipelinePage 加载插件列表失败无任何用户提示，FilesPage 文件读取/保存失败无 UI 反馈，ConfigPage JSON 解析失败返回空对象无错误提示。

所在文件

• gui/src/pages/PipelinePage.tsx:20
• gui/src/pages/FilesPage.tsx:362, 380, 391
• gui/src/pages/ConfigPage.tsx:37

建议修复

至少添加 toast/notification 提示用户操作失败，保留错误日志。

[TrueNine]

Fix: Replace silent error swallowing with user-visible notifications 🔔

Changes

Added a lightweight ToastProvider (zero extra deps, React Context + Tailwind) and wired it into the root component so all pages can surface errors.

File	What was fixed
PipelinePage.tsx:20	listAdaptors failure — now logs + shows "Failed to load plugins" toast
FilesPage.tsx:362	File read failure in handleSelect — now logs + shows "Failed to load file" toast
FilesPage.tsx:380	Save failure in handleSaveSource — now logs + shows "Failed to save file" toast
FilesPage.tsx:391	Save failure in handleSaveTranslated — now logs + shows "Failed to save file" toast
ConfigPage.tsx:37	JSON parse failure in parseConfig — now logs the error (console.error)

All error messages are i18n‑localized (zh‑CN / en‑US).