Implement file hash-based library matching and remove fuzzy ASIN matching

Adds file hash-based matching for Audiobookshelf library items to ensure 100% accurate ASIN assignment for RMAB-organized content. Removes fuzzy matching from library availability checks, making all matching ASIN-only to eliminate false positives and race conditions. Updates database schema, processors, and matcher utilities; adds new tests and documentation for the new matching strategy. Removes obsolete scripts, Dockerfile, and related tests; updates docker-compose for test environments.

src/app/admin/settings/tabs/AuthTab/AuthTab.tsx

@@ -74,6 +74,12 @@ export function AuthTab({
     !settings.registration.enabled &&
     !settings.hasLocalUsers;
 
+  // Check if only manual registration is enabled but no admin users exist
+  const showNoAdminWarning = settings.backendMode === 'audiobookshelf' &&
+    !settings.oidc.enabled &&
+    settings.registration.enabled &&
+    !settings.hasLocalAdmins;
+
   // Check if registration is disabled but local users can still log in
   const showRegistrationDisabledInfo = settings.backendMode === 'audiobookshelf' &&
     !settings.oidc.enabled &&
@@ -122,6 +128,26 @@ export function AuthTab({
         </div>
       )}
 
+      {/* Warning: Only manual registration enabled but no admin users exist */}
+      {showNoAdminWarning && (
+        <div className="bg-red-50 dark:bg-red-900/20 border border-red-200 dark:border-red-800 rounded-lg p-4">
+          <div className="flex gap-3">
+            <svg className="w-5 h-5 text-red-500 flex-shrink-0 mt-0.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z" />
+            </svg>
+            <div>
+              <h3 className="text-sm font-semibold text-red-800 dark:text-red-200">
+                No Admin Users Exist
+              </h3>
+              <p className="text-sm text-red-700 dark:text-red-300 mt-1">
+                Manual registration is enabled but no local admin users exist. New users will be able to register but you will be locked out of admin features.
+                Please enable OIDC or ensure at least one local admin user exists before saving.
+              </p>
+            </div>
+          </div>
+        </div>
+      )}
+
       {/* Info: Registration disabled but local users can still log in */}
       {showRegistrationDisabledInfo && (
         <div className="bg-blue-50 dark:bg-blue-900/20 border border-blue-200 dark:border-blue-800 rounded-lg p-4">