Add PDF translation API, utilities, docs, and config

Introduces core backend and frontend infrastructure for a PDF translation interface. Adds API endpoints for translation, PDF testing, and AI provider testing; implements PDF text extraction, cost tracking, and pricing logic in the lib directory; adds reusable UI components; and provides comprehensive documentation (SDD, environment setup, Claude instructions). Updates Tailwind and global styles, and includes a sample test PDF and configuration files.

app/api/test-pdf/route.ts

@@ -0,0 +1,42 @@
+import { NextRequest, NextResponse } from "next/server"
+import { extractTextFromPDF } from "@/lib/pdf-processor"
+
+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 provided" }, { status: 400 })
+    }
+    
+    if (file.type !== "application/pdf") {
+      return NextResponse.json({ error: "File must be PDF" }, { status: 400 })
+    }
+    
+    console.log(`Testing PDF: ${file.name}, size: ${file.size} bytes`)
+    
+    const arrayBuffer = await file.arrayBuffer()
+    const buffer = Buffer.from(arrayBuffer)
+    
+    const result = await extractTextFromPDF(buffer)
+    
+    return NextResponse.json({
+      success: true,
+      result: {
+        text: result.text,
+        textLength: result.text.length,
+        pageCount: result.pageCount,
+        isScanned: result.isScanned,
+        metadata: result.metadata
+      }
+    })
+    
+  } catch (error) {
+    console.error("PDF test error:", error)
+    return NextResponse.json({ 
+      error: `PDF test failed: ${error instanceof Error ? error.message : 'Unknown error'}`,
+      details: error instanceof Error ? error.stack : undefined
+    }, { status: 500 })
+  }
+}