feat: Add OCR Processing Layers Viewer UI and log proxy middleware

backend/pfm-web-app/src/utils/active-log.ts

@@ -0,0 +1,51 @@
+// Active Log Tracker for OCR Processing Layers
+
+export interface VllmCall {
+  request: any;
+  response: any;
+  timestamp: string;
+}
+
+export interface ActiveUploadLog {
+  filename: string;
+  vllm_calls: VllmCall[];
+  ocr_raw?: any;
+  stage_1_output?: any;
+  stage_2_output?: any;
+  frontend_response?: any;
+}
+
+// Store active log in global context to persist across Next.js hot-reloads
+const globalForActiveLog = global as unknown as {
+  activeLog: ActiveUploadLog | null;
+};
+
+export function startActiveLog(filename: string) {
+  globalForActiveLog.activeLog = {
+    filename,
+    vllm_calls: []
+  };
+  console.log(`[ActiveLog] Started tracking log for ${filename}`);
+}
+
+export function logVllmCall(request: any, response: any) {
+  if (globalForActiveLog.activeLog) {
+    globalForActiveLog.activeLog.vllm_calls.push({
+      request,
+      response,
+      timestamp: new Date().toISOString()
+    });
+    console.log(`[ActiveLog] Logged vLLM call for ${globalForActiveLog.activeLog.filename} (total calls: ${globalForActiveLog.activeLog.vllm_calls.length})`);
+  } else {
+    console.log("[ActiveLog] Warning: Attempted to log vLLM call but no active log session is running.");
+  }
+}
+
+export function getActiveLog(): ActiveUploadLog | null {
+  return globalForActiveLog.activeLog;
+}
+
+export function clearActiveLog() {
+  globalForActiveLog.activeLog = null;
+  console.log("[ActiveLog] Cleared active log tracking context");
+}