feat: add attachment upload UI and local file upload endpoint

- Add attachment button, file picker, and preview area to ChatInput
- Render image/file attachments in user message bubbles (MessageItem)
- Add Attachment type and attachments field to Message interface
- Add POST /__upload endpoint to both Vite dev server and production server
  for saving files to temp directory and returning local file paths
- Translate README to English

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vite.config.ts

@@ -2,6 +2,10 @@ import { defineConfig } from 'vite'
 import vue from '@vitejs/plugin-vue'
 import type { ProxyOptions } from 'vite'
 import { resolve } from 'path'
+import type { IncomingMessage, ServerResponse } from 'http'
+import { mkdir, writeFile } from 'fs/promises'
+import { tmpdir } from 'os'
+import { randomBytes } from 'crypto'
 
 function createProxyConfig(): ProxyOptions {
   return {
@@ -21,8 +25,74 @@ function createProxyConfig(): ProxyOptions {
   }
 }
 
+const UPLOAD_DIR = resolve(tmpdir(), 'hermes-uploads')
+
+async function handleUpload(req: IncomingMessage, res: ServerResponse) {
+  if (req.method !== 'POST') {
+    res.writeHead(405, { 'Content-Type': 'application/json' })
+    res.end(JSON.stringify({ error: 'Method not allowed' }))
+    return
+  }
+
+  const contentType = req.headers['content-type'] || ''
+  if (!contentType.startsWith('multipart/form-data')) {
+    res.writeHead(400, { 'Content-Type': 'application/json' })
+    res.end(JSON.stringify({ error: 'Expected multipart/form-data' }))
+    return
+  }
+
+  try {
+    await mkdir(UPLOAD_DIR, { recursive: true })
+    const chunks: Buffer[] = []
+    for await (const chunk of req) chunks.push(chunk)
+    const body = Buffer.concat(chunks).toString()
+
+    const boundary = '--' + contentType.split('boundary=')[1]
+    const parts = body.split(boundary).slice(1, -1)
+
+    const results: { name: string; path: string }[] = []
+    for (const part of parts) {
+      const headerEnd = part.indexOf('\r\n\r\n')
+      if (headerEnd === -1) continue
+      const header = part.substring(0, headerEnd)
+      const data = part.substring(headerEnd + 4, part.length - 2)
+
+      const filenameMatch = header.match(/filename="([^"]+)"/)
+      if (!filenameMatch) continue
+
+      const filename = filenameMatch[1]
+      const ext = filename.includes('.') ? '.' + filename.split('.').pop() : ''
+      const savedName = randomBytes(8).toString('hex') + ext
+      const savedPath = resolve(UPLOAD_DIR, savedName)
+
+      await writeFile(savedPath, Buffer.from(data, 'binary'))
+      results.push({ name: filename, path: savedPath })
+    }
+
+    res.writeHead(200, { 'Content-Type': 'application/json' })
+    res.end(JSON.stringify({ files: results }))
+  } catch (err: any) {
+    res.writeHead(500, { 'Content-Type': 'application/json' })
+    res.end(JSON.stringify({ error: err.message }))
+  }
+}
+
 export default defineConfig({
-  plugins: [vue()],
+  plugins: [
+    vue(),
+    {
+      name: 'upload-middleware',
+      configureServer(server) {
+        server.middlewares.use((req, res, next) => {
+          if (req.url?.startsWith('/__upload')) {
+            handleUpload(req as any, res as any)
+          } else {
+            next()
+          }
+        })
+      },
+    },
+  ],
   resolve: {
     alias: {
       '@': resolve(__dirname, 'src'),