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Replaces outdated Audiobookshelf API token instructions with new API key generation steps across documentation and UI.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.

src/app/setup/steps/AudiobookshelfStep.tsx

@@ -136,7 +136,7 @@ export function AudiobookshelfStep({
             onChange={(e) => onUpdate('absApiToken', e.target.value)}
           />
           <p className="text-sm text-gray-500 dark:text-gray-400 mt-1">
-            Find this in Audiobookshelf → Settings → Users → Your User → API Token
+            Generate this in Audiobookshelf → Settings → API Keys → Add API Key
           </p>
         </div>
 
@@ -270,8 +270,8 @@ export function AudiobookshelfStep({
               About API Token
             </p>
             <p className="text-sm text-blue-700 dark:text-blue-300 mt-1">
-              You can generate an API token in Audiobookshelf by going to Settings → Users
-              → selecting your user → and copying the API Token.
+              Generate an API key in Audiobookshelf by navigating to Settings → API Keys → Add API Key.
+              Give it a descriptive name and copy the generated key to use here.
             </p>
           </div>
         </div>