Implement chapter merging feature and update ranking algorithm

Added automatic chapter merging to M4B with admin/config toggles, UI controls, and backend logic. Updated documentation to reflect implementation. Refactored ranking algorithm: increased Title/Author match points, removed size scoring, and improved Usenet/torrent handling. Enhanced Prowlarr integration for protocol detection and filtering. Improved file organizer to support chapter merging. Various bug fixes and logging improvements.

src/app/setup/page.tsx

@@ -84,6 +84,7 @@ interface SetupState {
   downloadDir: string;
   mediaDir: string;
   metadataTaggingEnabled: boolean;
+  chapterMergingEnabled: boolean;
   bookdateProvider: string;
   bookdateApiKey: string;
   bookdateModel: string;
@@ -153,6 +154,7 @@ export default function SetupWizard() {
     downloadDir: '/downloads',
     mediaDir: '/media/audiobooks',
     metadataTaggingEnabled: true,
+    chapterMergingEnabled: false,
     bookdateProvider: 'openai',
     bookdateApiKey: '',
     bookdateModel: '',
@@ -228,6 +230,7 @@ export default function SetupWizard() {
           download_dir: state.downloadDir,
           media_dir: state.mediaDir,
           metadata_tagging_enabled: state.metadataTaggingEnabled,
+          chapter_merging_enabled: state.chapterMergingEnabled,
         },
         bookdate: state.bookdateConfigured ? {
           provider: state.bookdateProvider,
@@ -525,6 +528,7 @@ export default function SetupWizard() {
           downloadDir={state.downloadDir}
           mediaDir={state.mediaDir}
           metadataTaggingEnabled={state.metadataTaggingEnabled}
+          chapterMergingEnabled={state.chapterMergingEnabled}
           onUpdate={updateField}
           onNext={() => goToStep(currentStepNumber + 1)}
           onBack={() => goToStep(currentStepNumber - 1)}

src/app/setup/steps/PathsStep.tsx

@@ -13,6 +13,7 @@ interface PathsStepProps {
   downloadDir: string;
   mediaDir: string;
   metadataTaggingEnabled: boolean;
+  chapterMergingEnabled: boolean;
   onUpdate: (field: string, value: string | boolean) => void;
   onNext: () => void;
   onBack: () => void;
@@ -22,6 +23,7 @@ export function PathsStep({
   downloadDir,
   mediaDir,
   metadataTaggingEnabled,
+  chapterMergingEnabled,
   onUpdate,
   onNext,
   onBack,
@@ -235,6 +237,31 @@ export function PathsStep({
           </div>
         </div>
 
+        {/* Chapter Merging Toggle */}
+        <div className="bg-gray-50 dark:bg-gray-800 rounded-lg p-4 border border-gray-200 dark:border-gray-700">
+          <div className="flex items-start gap-4">
+            <input
+              type="checkbox"
+              id="chapter-merging"
+              checked={chapterMergingEnabled}
+              onChange={(e) => onUpdate('chapterMergingEnabled', e.target.checked)}
+              className="mt-1 h-5 w-5 rounded border-gray-300 text-blue-600 focus:ring-blue-500"
+            />
+            <div className="flex-1">
+              <label
+                htmlFor="chapter-merging"
+                className="block text-sm font-medium text-gray-900 dark:text-gray-100 cursor-pointer"
+              >
+                Auto-merge chapters to M4B
+              </label>
+              <p className="text-sm text-gray-600 dark:text-gray-400 mt-1">
+                Automatically merge multi-file chapter downloads into a single M4B audiobook with chapter
+                markers. Improves playback experience and library organization.
+              </p>
+            </div>
+          </div>
+        </div>
+
         <Button
           onClick={testPaths}
           loading={testing}