Update Audiobookshelf API key instructions and improve chapter merging

Replaces outdated Audiobookshelf API token instructions with new API key generation steps across documentation and UI. Enhances chapter merging logic to detect and handle book titles in metadata, prioritizing filename extraction for chapter names, and updates logging and documentation to reflect these changes. Adds ASIN copy-to-clipboard feature in AudiobookDetailsModal.

documentation/features/audiobookshelf-implementation-guide.md

@@ -1771,7 +1771,7 @@ export function AudiobookshelfStep({
             className="w-full px-3 py-2 border rounded-lg"
           />
           <p className="text-xs text-gray-500 mt-1">
-            Find this in Audiobookshelf → Settings → Users → Your User → API Token
+            Generate this in Audiobookshelf → Settings → API Keys → Add API Key
           </p>
         </div>