Fix hardcoded processing strategy in document controller

The confirmUpload and inline processing paths were hardcoded to
'document_ai_agentic_rag', ignoring the config setting. Now reads
from config.processingStrategy so the single-pass processor is
actually used when configured.

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

backend/src/controllers/documentController.ts

@@ -217,7 +217,7 @@ export const documentController = {
           document_id: documentId,
           user_id: userId,
           options: {
-            strategy: 'document_ai_agentic_rag',
+            strategy: config.processingStrategy || 'single_pass_quality_check',
           },
           max_attempts: 3,
         });
@@ -451,9 +451,10 @@ export const documentController = {
           const { unifiedDocumentProcessor } = await import('../services/unifiedDocumentProcessor');
           
           const processingStartTime = Date.now();
+          const activeStrategy = config.processingStrategy || 'single_pass_quality_check';
           logger.info('Calling unifiedDocumentProcessor.processDocument', {
             documentId,
-            strategy: 'document_ai_agentic_rag',
+            strategy: activeStrategy,
             fileSize: fileBuffer.length,
             correlationId
           });
@@ -461,9 +462,9 @@ export const documentController = {
           const result = await unifiedDocumentProcessor.processDocument(
             documentId,
             userId,
-            '', // Text is not needed for this strategy
+            '', // Text will be extracted from fileBuffer
             {
-              strategy: 'document_ai_agentic_rag',
+              strategy: activeStrategy,
               fileBuffer: fileBuffer,
               fileName: document.original_file_name,
               mimeType: 'application/pdf'