feat: remove markdown_based workflow option from UI

Mineru/Docling PDF parsing requires tokens or heavy deps not available
on client server. Remove the option from dropdown, default to docx,
and stop auto-selecting markdown_based for unrecognized file types.

docutranslate/static/index.html

@@ -261,7 +261,6 @@
                                     <div class="accordion-body">
                                         <select class="form-select" v-model="form.workflow_type"
                                                 @change="saveSetting('translator_last_workflow', form.workflow_type)">
-                                            <option value="markdown_based">{{ t('workflowOptionMarkdown') }}</option>
                                             <option value="docx">{{ t('workflowOptionDocx') }}</option>
                                             <option value="xlsx">{{ t('workflowOptionXlsx') }}</option>
                                             <option value="epub">{{ t('workflowOptionEpub') }}</option>
@@ -1097,7 +1096,7 @@
 
             // Form Data
             const form = reactive({
-                workflow_type: 'markdown_based',
+                workflow_type: 'docx',
                 auto_workflow_enabled: true,
                 convert_engine: 'mineru',
                 mineru_token: '',
@@ -1631,11 +1630,13 @@
                             pptx: 'pptx',
                             ppt: 'pptx'
                         };
-                        const newWorkflow = map[ext] || 'markdown_based';
+                        const newWorkflow = map[ext];
+                        if (newWorkflow) {
                             form.workflow_type = newWorkflow;
                             saveSetting('translator_last_workflow', newWorkflow);
                         }
                     }
+                }
             };
             const handleTaskFileDrop = (e, task) => handleTaskFileSelect(e, task);