chore: clean up repo for public release

- Remove BMAD framework, IDE configs, dev screenshots, test files,
  internal docs, and backup files
- Rename keep-notes/ to memento-note/
- Update all references from keep-notes to memento-note
- Add Apache 2.0 license with Commons Clause (non-commercial restriction)
- Add clean .gitignore and .env.docker.example

memento-note/app/api/upload/route.ts

@@ -0,0 +1,38 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { writeFile, mkdir } from 'fs/promises'
+import path from 'path'
+import { randomUUID } from 'crypto'
+
+export async function POST(request: NextRequest) {
+  try {
+    const formData = await request.formData()
+    const file = formData.get('file') as File
+
+    if (!file) {
+      return NextResponse.json(
+        { error: 'No file uploaded' },
+        { status: 400 }
+      )
+    }
+
+    const buffer = Buffer.from(await file.arrayBuffer())
+    const filename = `${randomUUID()}${path.extname(file.name)}`
+    
+    // Ensure directory exists
+    const uploadDir = path.join(process.cwd(), 'public/uploads/notes')
+    await mkdir(uploadDir, { recursive: true })
+    
+    const filePath = path.join(uploadDir, filename)
+    await writeFile(filePath, buffer)
+
+    return NextResponse.json({ 
+      success: true, 
+      url: `/uploads/notes/${filename}` 
+    })
+  } catch (error) {
+    return NextResponse.json(
+      { error: 'Failed to upload file' },
+      { status: 500 }
+    )
+  }
+}